fix: markdown rendering improvements

Improvements to markdown rendering in notification emails: - More consistent escaping of values interpolated into notification templates - Stricter link handling in the notification email renderer, scoped to the notification rendering path - HTML escaping of values interpolated into the outer email template - Expanded unit and end-to-end coverage of the notification rendering pipeline - `make gen` run to regenerate golden files for SMTP and webhook notification templates
2026-09-24 15:04:27 +08:00 · 2026-08-10 10:45:19 +02:00
parent 192842c8f2
commit 07f79af65b
37 changed files with 962 additions and 70 deletions
@@ -66,7 +66,7 @@ func (s *SMTPHandler) Dispatcher(payload types.MessagePayload, titleTmpl, bodyTm
 		return nil, xerrors.Errorf("render subject: %w", err)
 	}

-	htmlBody := markdown.HTMLFromMarkdown(bodyTmpl)
+	htmlBody := markdown.HTMLFromMarkdownSafe(bodyTmpl)
 	plainBody, err := markdown.PlaintextFromMarkdown(bodyTmpl)
 	if err != nil {
 		return nil, xerrors.Errorf("render plaintext body: %w", err)
@@ -3,7 +3,7 @@
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-    <title>{{ .Labels._subject }}</title>
+    <title>{{ .Labels._subject | html }}</title>
  </head>
  <body style="margin: 0; padding: 0; font-family: -apple-system, system-ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell', 'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif; color: #020617; background: #f8fafc;">
    <div style="max-width: 600px; margin: 20px auto; padding: 60px; border: 1px solid #e2e8f0; border-radius: 8px; background-color: #fff; text-align: left; font-size: 14px; line-height: 1.5;">
@@ -11,16 +11,16 @@
        <img src="{{ logo_url | html }}" alt="{{ app_name | html }} Logo" style="height: 40px;" />
      </div>
      <h1 style="text-align: center; font-size: 24px; font-weight: 400; margin: 8px 0 32px; line-height: 1.5;">
-        {{ .Labels._subject }}
+        {{ .Labels._subject | html }}
      </h1>
      <div style="line-height: 1.5;">
-        <p>Hi {{ .UserName }},</p>
+        <p>Hi {{ .UserName | html }},</p>
        {{ .Labels._body }}
      </div>
      <div style="text-align: center; margin-top: 32px;">
        {{ range $action := .Actions }}
-        <a href="{{ $action.URL }}" style="display: inline-block; padding: 13px 24px; background-color: #020617; color: #f8fafc; text-decoration: none; border-radius: 8px; margin: 0 4px;">
-          {{ $action.Label }}
+        <a href="{{ $action.URL | html }}" style="display: inline-block; padding: 13px 24px; background-color: #020617; color: #f8fafc; text-decoration: none; border-radius: 8px; margin: 0 4px;">
+          {{ $action.Label | html }}
        </a>
        {{ end }}
      </div>
@@ -7,6 +7,8 @@ import (

 	"github.com/stretchr/testify/require"

+	markdown "github.com/coder/coder/v2/coderd/render"
+
 	"github.com/coder/coder/v2/coderd/notifications/render"
 	"github.com/coder/coder/v2/coderd/notifications/types"
 )
@@ -43,6 +45,354 @@ func TestSMTPHTMLTemplateEscapesAppearanceHelpers(t *testing.T) {
 	require.False(t, strings.Contains(got, logoURL), "raw logo URL must not be rendered")
 }

+// TestSMTPHTMLTemplateMarkdownInjection is an end-to-end regression test that
+// exercises the full notification email rendering pipeline with malicious input.
+// It simulates the complete flow: SanitizePayload -> GoTemplate (body) ->
+// HTMLFromMarkdownSafe -> GoTemplate (outer HTML template) and asserts that the
+// final HTML email output contains no attacker-controlled links, headings, images,
+// scripts, or other injected content.
+//
+// If this test fails, it likely means a change to the rendering pipeline has
+// introduced a Markdown or HTML injection vulnerability in notification emails.
+func TestSMTPHTMLTemplateMarkdownInjection(t *testing.T) {
+	t.Parallel()
+
+	helpers := map[string]any{
+		"base_url":     func() string { return "https://coder.example.com" },
+		"current_year": func() string { return "2026" },
+		"logo_url":     func() string { return "https://coder.example.com/logo.png" },
+		"app_name":     func() string { return "Coder" },
+	}
+
+	tests := []struct {
+		name string
+		// payload is the unsanitized notification payload (as it would arrive
+		// from the database before SanitizePayload runs).
+		payload types.MessagePayload
+		// bodyTemplate is the notification body template (stored in the DB).
+		bodyTemplate string
+		// absentInHTML lists substrings that must NOT appear in the final HTML
+		// email output.
+		absentInHTML []string
+		// presentInHTML lists substrings that MUST appear in the final HTML.
+		presentInHTML []string
+	}{
+		{
+			name: "markdown link injection via display name",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "Eve\n[Re-authenticate](https://evil.example/login)",
+				Labels: map[string]string{
+					"created_account_user_name": "Eve\n[Re-authenticate](https://evil.example/login)",
+					"initiator":                 "admin",
+				},
+			},
+			bodyTemplate: `Account created for **{{.Labels.created_account_user_name}}** by **{{.Labels.initiator}}**.`,
+			absentInHTML: []string{
+				`<a href="https://evil.example`,
+				`href="https://evil.example`,
+			},
+			presentInHTML: []string{
+				"<strong>admin</strong>",
+			},
+		},
+		{
+			name: "heading injection via display name",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "Eve\n## URGENT SECURITY ALERT",
+				Labels: map[string]string{
+					"suspended_account_user_name": "Eve\n## URGENT SECURITY ALERT",
+					"initiator":                   "admin",
+				},
+			},
+			bodyTemplate: `Account **{{.Labels.suspended_account_user_name}}** suspended by **{{.Labels.initiator}}**.`,
+			absentInHTML: []string{
+				"<h2>",
+				"<h1>",
+				"<h3>",
+			},
+			presentInHTML: []string{
+				"## URGENT SECURITY ALERT", // rendered as literal text
+			},
+		},
+		{
+			name: "image tracking pixel injection",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "![](https://evil.example/track.gif)",
+				Labels: map[string]string{
+					"name": "![](https://evil.example/track.gif)",
+				},
+			},
+			bodyTemplate: `Workspace **{{.Labels.name}}** deleted.`,
+			absentInHTML: []string{
+				`src="https://evil.example`, // no attacker-controlled image source
+			},
+			presentInHTML: []string{
+				"![]", // rendered as literal text
+			},
+		},
+		{
+			name: "javascript URI via markdown link",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "normal",
+				Labels: map[string]string{
+					"name": "[xss](javascript:alert(document.cookie))",
+				},
+			},
+			bodyTemplate: `Workspace **{{.Labels.name}}** updated.`,
+			absentInHTML: []string{
+				`href="javascript:`, // no javascript link
+			},
+		},
+		{
+			name: "raw HTML injection in display name",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               `<script>alert(1)</script>`,
+				Labels:                 map[string]string{},
+			},
+			bodyTemplate: `Hello.`,
+			absentInHTML: []string{
+				"<script>", // raw script tag must not appear
+			},
+		},
+		{
+			name: "bare URL autolink in label value",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "admin",
+				Labels: map[string]string{
+					"name": "workspace https://evil.example test",
+				},
+			},
+			bodyTemplate: `Workspace **{{.Labels.name}}** created.`,
+			absentInHTML: []string{
+				`<a href="https://evil.example"`,
+			},
+		},
+		{
+			// Regression: CommonMark angle-bracket autolink via display name.
+			// Escaping ">" alone did not stop this ("<" was never escaped).
+			name: "angle-bracket autolink via display name",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "<https://evil.example/login>",
+				Labels: map[string]string{
+					"created_account_user_name": "<https://evil.example/login>",
+					"initiator":                 "admin",
+				},
+			},
+			bodyTemplate: `Account created for **{{.Labels.created_account_user_name}}** by **{{.Labels.initiator}}**.`,
+			absentInHTML: []string{
+				`href="https://evil.example`,
+			},
+			presentInHTML: []string{
+				"<strong>admin</strong>",
+			},
+		},
+		{
+			// Regression: the backslash-tweaked bypass of the angle-bracket
+			// autolink escape. A user backslash combined with the sanitizer's
+			// "\>" left a live autolink terminator until "\" was also escaped.
+			name: "backslash-tweaked autolink bypass via display name",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "<https://evil.example/login\\>",
+				Labels: map[string]string{
+					"created_account_user_name": "<https://evil.example/login\\>",
+					"initiator":                 "admin",
+				},
+			},
+			bodyTemplate: `Account created for **{{.Labels.created_account_user_name}}** by **{{.Labels.initiator}}**.`,
+			absentInHTML: []string{
+				`href="https://evil.example`,
+			},
+			presentInHTML: []string{
+				"<strong>admin</strong>",
+			},
+		},
+		{
+			name: "legitimate template content renders correctly",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "John Smith",
+				Labels: map[string]string{
+					"workspace": "my-dev-env",
+					"initiator": "admin",
+				},
+			},
+			bodyTemplate: `Workspace **{{.Labels.workspace}}** was updated by **{{.Labels.initiator}}**.`,
+			presentInHTML: []string{
+				"Hi John Smith,",
+				"<strong>my-dev-env</strong>",
+				"<strong>admin</strong>",
+			},
+		},
+		{
+			name: "unicode display name preserved",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "Jos\u00e9 Garc\u00eda",
+				Labels:                 map[string]string{"name": "workspace-1"},
+			},
+			bodyTemplate: `Workspace **{{.Labels.name}}** ready.`,
+			presentInHTML: []string{
+				"Jos\u00e9 Garc\u00eda",
+				"<strong>workspace-1</strong>",
+			},
+		},
+		// Legitimate rendering regression tests below. These verify that
+		// production notification features continue working after the
+		// security hardening.
+		{
+			name: "template-authored markdown link renders correctly",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "user",
+				Labels: map[string]string{
+					"name":   "my-workspace",
+					"reason": "inactivity",
+				},
+			},
+			bodyTemplate: `Your workspace **{{.Labels.name}}** has been marked as [**dormant**](https://coder.com/docs/templates/schedule#dormancy-threshold-enterprise) because of {{.Labels.reason}}.`,
+			presentInHTML: []string{
+				`<a href="https://coder.com/docs/templates/schedule#dormancy-threshold-enterprise">`,
+				"<strong>dormant</strong>",
+				"<strong>my-workspace</strong>",
+			},
+		},
+		{
+			name: "markdown list renders correctly",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "admin",
+				Labels:                 map[string]string{},
+			},
+			bodyTemplate: "Build failures:\n\n- **template-v1** failed 3 times\n- **template-v2** failed 1 time",
+			presentInHTML: []string{
+				"<li>",
+				"<strong>template-v1</strong>",
+				"<strong>template-v2</strong>",
+			},
+		},
+		{
+			name: "emphasis and code spans render correctly",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "admin",
+				Labels: map[string]string{
+					"workspace": "my-ws",
+				},
+			},
+			bodyTemplate: "Volume **`/home/coder`** is over 90%% full in workspace **{{.Labels.workspace}}**.",
+			presentInHTML: []string{
+				"<code>/home/coder</code>",
+				"<strong>my-ws</strong>",
+			},
+		},
+		{
+			name: "action buttons render with proper URLs",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "user",
+				Labels:                 map[string]string{},
+				Actions: []types.TemplateAction{
+					{Label: "View workspace", URL: "https://coder.example.com/@user/my-workspace"},
+					{Label: "View template", URL: "https://coder.example.com/templates/docker"},
+				},
+			},
+			bodyTemplate: `Your workspace is ready.`,
+			presentInHTML: []string{
+				`href="https://coder.example.com/@user/my-workspace"`,
+				"View workspace",
+				`href="https://coder.example.com/templates/docker"`,
+				"View template",
+			},
+		},
+		{
+			name: "footer links and logo render correctly",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "user",
+				Labels:                 map[string]string{},
+			},
+			bodyTemplate: `Hello.`,
+			presentInHTML: []string{
+				// Footer links
+				`href="https://coder.example.com/settings/notifications"`,
+				"manage your notification settings",
+				"Stop receiving emails like this",
+				// Logo
+				`<img src="https://coder.example.com/logo.png"`,
+				// Copyright
+				"Coder. All rights reserved",
+			},
+		},
+		{
+			name: "conditional label rendering",
+			payload: types.MessagePayload{
+				NotificationTemplateID: "00000000-0000-0000-0000-000000000000",
+				UserName:               "admin",
+				Labels: map[string]string{
+					"created_account_name":      "newuser",
+					"created_account_user_name": "New User",
+					"initiator":                 "admin",
+				},
+			},
+			bodyTemplate: `New user account **{{.Labels.created_account_name}}** has been created.` + "\n\n" +
+				`This new user account was created {{if .Labels.created_account_user_name}}for **{{.Labels.created_account_user_name}}** {{end}}by **{{.Labels.initiator}}**.`,
+			presentInHTML: []string{
+				"<strong>newuser</strong>",
+				"<strong>New User</strong>",
+				"<strong>admin</strong>",
+				"for",
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			// Step 1: Render the body from a sanitized copy, leaving the
+			// payload itself raw (as notifier.prepare does).
+			sanitized := render.SanitizedPayload(tt.payload)
+
+			// Step 2: Render body template via GoTemplate
+			body, err := render.GoTemplate(tt.bodyTemplate, sanitized, nil)
+			require.NoError(t, err)
+
+			// Step 3: Convert markdown body to HTML (as SMTP dispatcher does)
+			htmlBody := markdown.HTMLFromMarkdownSafe(body)
+
+			// Step 4: Render subject via PlaintextFromMarkdown
+			subject := "Test notification"
+
+			// Step 5: Inject into outer HTML template using the raw payload (as
+			// the SMTP dispatcher does). The greeting interpolates the raw
+			// UserName, made safe by the template's `| html`, not by Markdown
+			// escaping.
+			tt.payload.Labels["_subject"] = subject
+			tt.payload.Labels["_body"] = htmlBody
+			finalHTML, err := render.GoTemplate(htmlTemplate, tt.payload, helpers)
+			require.NoError(t, err)
+
+			// Step 6: Assert on final HTML output
+			for _, s := range tt.absentInHTML {
+				require.False(t, strings.Contains(finalHTML, s),
+					"final HTML email must NOT contain %q", s)
+			}
+			for _, s := range tt.presentInHTML {
+				require.True(t, strings.Contains(finalHTML, s),
+					"final HTML email must contain %q", s)
+			}
+		})
+	}
+}
+
 func TestValidateFromAddr(t *testing.T) {
 	t.Parallel()

@@ -250,11 +250,20 @@ func (n *notifier) prepare(ctx context.Context, msg database.AcquireNotification
 		return nil, decorateHelpersError{err}
 	}

+	// Render the title and body from a sanitized copy so that user-controlled
+	// values (display names from OIDC claims, label values) cannot inject
+	// Markdown into the contexts that are subsequently Markdown-rendered: the
+	// SMTP HTML email and the react-markdown inbox. The original payload is
+	// passed to the dispatcher unmodified so that non-Markdown consumers (the
+	// webhook JSON, the SMTP greeting, and the plaintext email part) receive
+	// verbatim values rather than escaped ones.
+	sanitized := render.SanitizedPayload(payload)
+
 	var title, body string
-	if title, err = render.GoTemplate(msg.TitleTemplate, payload, helpers); err != nil {
+	if title, err = render.GoTemplate(msg.TitleTemplate, sanitized, helpers); err != nil {
 		return nil, xerrors.Errorf("render title: %w", err)
 	}
-	if body, err = render.GoTemplate(msg.BodyTemplate, payload, helpers); err != nil {
+	if body, err = render.GoTemplate(msg.BodyTemplate, sanitized, helpers); err != nil {
 		return nil, xerrors.Errorf("render body: %w", err)
 	}

@@ -13,6 +13,70 @@ import (
 // This string is not exported as a const from the text/template.
 const NoValue = "<no value>"

+// markdownReplacer escapes characters that have special meaning in Markdown.
+// This prevents user-controlled values (display names, labels) from being
+// interpreted as Markdown syntax when interpolated into notification body
+// templates that are subsequently rendered as HTML.
+var markdownReplacer = strings.NewReplacer(
+	// Escape the backslash first (conceptually): strings.NewReplacer performs a
+	// single non-overlapping left-to-right pass and never re-processes its own
+	// output, so a user-supplied "\" becomes a literal "\\" without touching the
+	// backslashes we introduce below.
+	"\\", "\\\\",
+	"[", "\\[",
+	"]", "\\]",
+	"(", "\\(",
+	")", "\\)",
+	"#", "\\#",
+	"!", "\\!",
+	"*", "\\*",
+	// Escape both angle brackets. ">" alone left "<...>" CommonMark autolinks
+	// exploitable (angle-bracket autolinks are core inline syntax, not the
+	// parser.Autolink extension, so disabling that extension does not stop
+	// them); escaping "<" prevents such an autolink from ever opening.
+	"<", "\\<",
+	">", "\\>",
+	"~", "\\~",
+	"`", "\\`",
+	"|", "\\|",
+	"_", "\\_",
+	"\n", " ",
+	"\r", "",
+)
+
+// SanitizeMarkdown escapes Markdown metacharacters in a string and
+// collapses newlines so that the value is rendered as literal text
+// when embedded in a Markdown document.
+func SanitizeMarkdown(s string) string {
+	return markdownReplacer.Replace(s)
+}
+
+// SanitizedPayload returns a copy of p with Markdown metacharacters escaped in
+// the user-controlled fields (UserName and Labels). Use the returned copy only
+// to render the title and body templates, whose output is subsequently passed
+// through a Markdown renderer (HTMLFromMarkdownSafe for the SMTP HTML email, and
+// react-markdown for the in-product inbox). Escaping there prevents display
+// names and label values from injecting Markdown such as links or headings.
+//
+// The original payload is left unmodified. Non-Markdown consumers must receive
+// the verbatim values: the webhook delivers payload.Labels and payload.UserName
+// as raw JSON, the SMTP greeting interpolates UserName as HTML (escaped by the
+// template's `| html`, not by Markdown escaping), and the plaintext email part
+// is not Markdown. Escaping those in place left literal backslashes in every one
+// of them.
+func SanitizedPayload(p types.MessagePayload) types.MessagePayload {
+	sanitized := p
+	sanitized.UserName = SanitizeMarkdown(p.UserName)
+	if p.Labels != nil {
+		// Copy the map so the caller's payload keeps its raw label values.
+		sanitized.Labels = make(map[string]string, len(p.Labels))
+		for k, v := range p.Labels {
+			sanitized.Labels[k] = SanitizeMarkdown(v)
+		}
+	}
+	return sanitized
+}
+
 // GoTemplate attempts to substitute the given payload into the given template using Go's templating syntax.
 // TODO: memoize templates for memory efficiency?
 func GoTemplate(in string, payload types.MessagePayload, extraFuncs template.FuncMap) (string, error) {
@@ -0,0 +1,333 @@
+package render_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/coder/coder/v2/coderd/notifications/render"
+	"github.com/coder/coder/v2/coderd/notifications/types"
+	coderrender "github.com/coder/coder/v2/coderd/render"
+)
+
+func TestSanitizeMarkdown(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name     string
+		input    string
+		contains []string // substrings the output must contain
+		absent   []string // substrings the output must NOT contain
+		exact    string   // exact expected output, empty to skip
+	}{
+		{
+			name:  "plain text unchanged",
+			input: "Hello World",
+			exact: "Hello World",
+		},
+		{
+			name:  "empty string",
+			input: "",
+			exact: "",
+		},
+		{
+			name:  "unicode names preserved",
+			input: "José García",
+			exact: "José García",
+		},
+		{
+			name:  "CJK names preserved",
+			input: "田中太郎",
+			exact: "田中太郎",
+		},
+		{
+			name:     "markdown link escaped",
+			input:    "[Click me](https://evil.example)",
+			absent:   []string{"[Click me]"},
+			contains: []string{"\\[", "\\]", "\\(", "\\)"},
+		},
+		{
+			name:     "heading injection escaped",
+			input:    "## URGENT heading",
+			absent:   []string{"## "},
+			contains: []string{"\\#\\# URGENT heading"},
+		},
+		{
+			name:     "image injection escaped",
+			input:    "![tracker](https://evil.example/pixel.gif)",
+			absent:   []string{"![tracker]("},
+			contains: []string{"\\!", "\\[tracker\\]"},
+		},
+		{
+			name:     "bold/italic escaped",
+			input:    "**bold** and *italic*",
+			contains: []string{"\\*\\*bold\\*\\*", "\\*italic\\*"},
+		},
+		{
+			name:  "newlines collapsed to spaces",
+			input: "line1\nline2\nline3",
+			exact: "line1 line2 line3",
+		},
+		{
+			name:  "carriage returns removed",
+			input: "line1\r\nline2",
+			exact: "line1 line2",
+		},
+		{
+			name:     "backtick code escaped",
+			input:    "`code block`",
+			contains: []string{"\\`code block\\`"},
+		},
+		{
+			name:     "pipe table escaped",
+			input:    "| col1 | col2 |",
+			contains: []string{"\\|"},
+		},
+		{
+			name:     "blockquote escaped",
+			input:    "> quoted text",
+			contains: []string{"\\>"},
+		},
+		{
+			name:     "underscore escaped",
+			input:    "_emphasis_",
+			contains: []string{"\\_emphasis\\_"},
+		},
+		{
+			name:     "full phishing payload",
+			input:    "Eve\n## URGENT: SSO certificate expiring\n[Re-authenticate now](https://coder-sso.attacker.example/login)",
+			absent:   []string{"\n", "[Re-authenticate now]"},
+			contains: []string{"Eve ", "\\#\\# URGENT"},
+		},
+		{
+			name:     "javascript URI in markdown link",
+			input:    "[Click](javascript:alert(1))",
+			absent:   []string{"[Click](javascript"},
+			contains: []string{"\\[Click\\]\\(javascript"},
+		},
+		{
+			name:  "parentheses in normal name",
+			input: "Jane (Admin)",
+			exact: "Jane \\(Admin\\)",
+		},
+		{
+			// Regression: angle-bracket autolink must not survive. Escaping ">"
+			// alone was insufficient because "<" was never escaped, so the
+			// "<...>" autolink still opened (SEC-93 / GHSA-2w2x-w3c8-9jrw
+			// follow-up). The escaped output still contains the "<" byte (as
+			// "\<"), so correctness is asserted via the exact escaped form here;
+			// the "no clickable <a href>" guarantee is covered end-to-end in
+			// TestSMTPHTMLTemplateMarkdownInjection.
+			name:  "angle-bracket autolink escaped",
+			input: "<https://evil.example/login>",
+			exact: "\\<https://evil.example/login\\>",
+		},
+		{
+			// Regression: the backslash-tweaked bypass. Without escaping "\",
+			// a user backslash combined with the sanitizer's own "\>" to leave
+			// a live autolink terminator.
+			name:  "backslash bypass of autolink escaped",
+			input: "<https://evil.example/login\\>",
+			exact: "\\<https://evil.example/login\\\\\\>",
+		},
+		{
+			name:  "lone backslash escaped",
+			input: "back\\slash",
+			exact: "back\\\\slash",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			result := render.SanitizeMarkdown(tt.input)
+
+			if tt.exact != "" {
+				assert.Equal(t, tt.exact, result)
+			}
+			for _, s := range tt.contains {
+				assert.Contains(t, result, s, "output should contain %q", s)
+			}
+			for _, s := range tt.absent {
+				assert.NotContains(t, result, s, "output should NOT contain %q", s)
+			}
+		})
+	}
+}
+
+func TestSanitizedPayload(t *testing.T) {
+	t.Parallel()
+
+	t.Run("sanitizes UserName and Labels in the copy", func(t *testing.T) {
+		t.Parallel()
+		payload := types.MessagePayload{
+			UserName:     "[evil](https://evil.example)",
+			UserEmail:    "user@example.com",
+			UserUsername: "normaluser",
+			Labels: map[string]string{
+				"initiator":                 "admin",
+				"created_account_user_name": "## Heading\n[link](https://evil.example)",
+				"safe_label":                "no-special-chars",
+			},
+		}
+		sanitized := render.SanitizedPayload(payload)
+
+		// UserName should be sanitized in the copy
+		assert.NotContains(t, sanitized.UserName, "[evil]")
+		assert.Contains(t, sanitized.UserName, "\\[evil\\]")
+
+		// Labels should be sanitized in the copy
+		assert.NotContains(t, sanitized.Labels["created_account_user_name"], "## Heading")
+		assert.Contains(t, sanitized.Labels["created_account_user_name"], "\\#\\# Heading")
+		assert.NotContains(t, sanitized.Labels["created_account_user_name"], "\n")
+
+		// Non-special labels unchanged
+		assert.Equal(t, "no-special-chars", sanitized.Labels["safe_label"])
+		assert.Equal(t, "admin", sanitized.Labels["initiator"])
+
+		// Fields NOT in scope are NOT modified
+		assert.Equal(t, "user@example.com", sanitized.UserEmail)
+		assert.Equal(t, "normaluser", sanitized.UserUsername)
+	})
+
+	t.Run("leaves the original payload untouched", func(t *testing.T) {
+		t.Parallel()
+		// The original must keep its raw values so non-Markdown consumers
+		// (webhook JSON, SMTP greeting, plaintext) receive them verbatim.
+		payload := types.MessagePayload{
+			UserName: "Jane (Admin)",
+			Labels: map[string]string{
+				"template_version": "angry_torvalds",
+			},
+		}
+		sanitized := render.SanitizedPayload(payload)
+
+		// Copy is escaped.
+		assert.Equal(t, "Jane \\(Admin\\)", sanitized.UserName)
+		assert.Equal(t, "angry\\_torvalds", sanitized.Labels["template_version"])
+
+		// Original is verbatim.
+		assert.Equal(t, "Jane (Admin)", payload.UserName)
+		assert.Equal(t, "angry_torvalds", payload.Labels["template_version"])
+	})
+
+	t.Run("handles nil labels map", func(t *testing.T) {
+		t.Parallel()
+		payload := types.MessagePayload{
+			UserName: "test",
+			Labels:   nil,
+		}
+		var sanitized types.MessagePayload
+		require.NotPanics(t, func() {
+			sanitized = render.SanitizedPayload(payload)
+		})
+		assert.Nil(t, sanitized.Labels)
+	})
+
+	t.Run("handles empty payload", func(t *testing.T) {
+		t.Parallel()
+		var sanitized types.MessagePayload
+		require.NotPanics(t, func() {
+			sanitized = render.SanitizedPayload(types.MessagePayload{})
+		})
+		assert.Equal(t, "", sanitized.UserName)
+	})
+}
+
+func TestSanitizeMarkdownInTemplateRendering(t *testing.T) {
+	t.Parallel()
+
+	// End-to-end: sanitize -> GoTemplate -> verify no injection in output
+	t.Run("malicious display name in body template", func(t *testing.T) {
+		t.Parallel()
+		payload := types.MessagePayload{
+			UserName: "Eve\n## URGENT\n[Click](https://evil.example)",
+			Labels: map[string]string{
+				"created_account_name":      "eviluser",
+				"created_account_user_name": "Eve\n## URGENT\n[Click](https://evil.example)",
+				"initiator":                 "admin",
+			},
+		}
+		sanitized := render.SanitizedPayload(payload)
+
+		bodyTmpl := `New user account **{{.Labels.created_account_name}}** has been created.
+
+This new user account was created {{if .Labels.created_account_user_name}}for **{{.Labels.created_account_user_name}}** {{end}}by **{{.Labels.initiator}}**.`
+
+		body, err := render.GoTemplate(bodyTmpl, sanitized, nil)
+		require.NoError(t, err)
+
+		// The rendered markdown should not contain unescaped link/heading syntax
+		assert.NotContains(t, body, "[Click](")
+		assert.NotContains(t, body, "## URGENT")
+		// Should still contain escaped versions
+		assert.Contains(t, body, "\\[Click\\]")
+	})
+
+	t.Run("bold formatting in template still works", func(t *testing.T) {
+		t.Parallel()
+		payload := types.MessagePayload{
+			Labels: map[string]string{
+				"name": "my-workspace",
+			},
+		}
+		sanitized := render.SanitizedPayload(payload)
+
+		body, err := render.GoTemplate(
+			`Workspace **{{.Labels.name}}** has been deleted.`,
+			sanitized, nil)
+		require.NoError(t, err)
+
+		// Template-level bold markers should survive (they're in the template, not labels)
+		assert.Contains(t, body, "**my-workspace**")
+	})
+
+	t.Run("label with asterisks does not break bold", func(t *testing.T) {
+		t.Parallel()
+		payload := types.MessagePayload{
+			Labels: map[string]string{
+				"name": "workspace*test",
+			},
+		}
+		sanitized := render.SanitizedPayload(payload)
+
+		body, err := render.GoTemplate(
+			`Workspace **{{.Labels.name}}** updated.`,
+			sanitized, nil)
+		require.NoError(t, err)
+
+		// The escaped asterisk in the value should not interfere with template bold
+		assert.Contains(t, body, `**workspace\*test**`)
+	})
+}
+
+func TestHTMLFromMarkdownSafe(t *testing.T) {
+	t.Parallel()
+
+	// Import the render package for HTMLFromMarkdownSafe
+	// We test it indirectly through the notification render package
+
+	t.Run("sanitized payload produces no links in final HTML", func(t *testing.T) {
+		t.Parallel()
+		payload := types.MessagePayload{
+			Labels: map[string]string{
+				"name": "[evil](https://evil.example)",
+			},
+		}
+		sanitized := render.SanitizedPayload(payload)
+
+		body, err := render.GoTemplate(
+			`Account **{{.Labels.name}}** created.`,
+			sanitized, nil)
+		require.NoError(t, err)
+
+		// Render the sanitized body to HTML exactly as the SMTP dispatcher
+		// does, and assert the attacker link never becomes an <a> tag. The URL
+		// still appears as inert literal text, which is fine; what matters is
+		// that it is not a clickable link.
+		html := coderrender.HTMLFromMarkdownSafe(body)
+		assert.NotContains(t, html, "<a", "sanitized body must not produce a link")
+		assert.Contains(t, html, "<strong>", "legitimate template formatting should still render")
+	})
+}
@@ -29,7 +29,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Task 'my-workspace' completed</title>
+    <title>Task &#39;my-workspace&#39; completed</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -44,7 +44,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Task 'my-workspace' completed
+        Task &#39;my-workspace&#39; completed
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -29,7 +29,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Task 'my-workspace' failed</title>
+    <title>Task &#39;my-workspace&#39; failed</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -44,7 +44,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Task 'my-workspace' failed
+        Task &#39;my-workspace&#39; failed
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -29,7 +29,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Task 'my-workspace' is idle</title>
+    <title>Task &#39;my-workspace&#39; is idle</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -44,7 +44,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Task 'my-workspace' is idle
+        Task &#39;my-workspace&#39; is idle
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -29,7 +29,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Task 'my-task' is paused</title>
+    <title>Task &#39;my-task&#39; is paused</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -44,7 +44,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Task 'my-task' is paused
+        Task &#39;my-task&#39; is paused
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -29,7 +29,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Task 'my-task' has resumed</title>
+    <title>Task &#39;my-task&#39; has resumed</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -44,7 +44,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Task 'my-task' has resumed
+        Task &#39;my-task&#39; has resumed
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -29,7 +29,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Task 'my-workspace' is working</title>
+    <title>Task &#39;my-workspace&#39; is working</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -44,7 +44,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Task 'my-workspace' is working
+        Task &#39;my-workspace&#39; is working
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -27,7 +27,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Template "Bobby's Template" deleted</title>
+    <title>Template &#34;Bobby&#39;s Template&#34; deleted</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -42,7 +42,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Template "Bobby's Template" deleted
+        Template &#34;Bobby&#39;s Template&#34; deleted
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -35,7 +35,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Template 'alpha' has been deprecated</title>
+    <title>Template &#39;alpha&#39; has been deprecated</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -50,7 +50,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Template 'alpha' has been deprecated
+        Template &#39;alpha&#39; has been deprecated
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -29,7 +29,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>User account "bobby" activated</title>
+    <title>User account &#34;bobby&#34; activated</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -44,7 +44,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        User account "bobby" activated
+        User account &#34;bobby&#34; activated
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -29,7 +29,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>User account "bobby" created</title>
+    <title>User account &#34;bobby&#34; created</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -44,7 +44,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        User account "bobby" created
+        User account &#34;bobby&#34; created
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -29,7 +29,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>User account "bobby" deleted</title>
+    <title>User account &#34;bobby&#34; deleted</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -44,7 +44,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        User account "bobby" deleted
+        User account &#34;bobby&#34; deleted
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -30,7 +30,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>User account "bobby" suspended</title>
+    <title>User account &#34;bobby&#34; suspended</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -45,7 +45,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        User account "bobby" suspended
+        User account &#34;bobby&#34; suspended
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -56,10 +56,10 @@ argin: 8px 0 32px; line-height: 1.5;">
      <div style=3D"text-align: center; margin-top: 32px;">
       =20
        <a href=3D"http://test.com/reset-password/change?otp=3Dfad9020b-656=
-2-4cdb-87f1-0486f1bea415&email=3Dbobby%2Fdrop-table%2Buser%40coder.com" sty=
-le=3D"display: inline-block; padding: 13px 24px; background-color: #020617;=
- color: #f8fafc; text-decoration: none; border-radius: 8px; margin: 0 4px;"=
->
+2-4cdb-87f1-0486f1bea415&amp;email=3Dbobby%2Fdrop-table%2Buser%40coder.com"=
+ style=3D"display: inline-block; padding: 13px 24px; background-color: #020=
+617; color: #f8fafc; text-decoration: none; border-radius: 8px; margin: 0 4=
+px;">
          Reset password
        </a>
       =20
@@ -30,7 +30,8 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Workspace "bobby-workspace" updated automatically</title>
+    <title>Workspace &#34;bobby-workspace&#34; updated automatically</title=
+>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -45,7 +46,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Workspace "bobby-workspace" updated automatically
+        Workspace &#34;bobby-workspace&#34; updated automatically
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -29,7 +29,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Workspace "bobby-workspace" autobuild failed</title>
+    <title>Workspace &#34;bobby-workspace&#34; autobuild failed</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -44,7 +44,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Workspace "bobby-workspace" autobuild failed
+        Workspace &#34;bobby-workspace&#34; autobuild failed
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -29,7 +29,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Your workspace "bobby-workspace" will stop soon</title>
+    <title>Your workspace &#34;bobby-workspace&#34; will stop soon</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -44,7 +44,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Your workspace "bobby-workspace" will stop soon
+        Your workspace &#34;bobby-workspace&#34; will stop soon
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -28,7 +28,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Workspace 'bobby-workspace' has been created</title>
+    <title>Workspace &#39;bobby-workspace&#39; has been created</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -43,7 +43,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Workspace 'bobby-workspace' has been created
+        Workspace &#39;bobby-workspace&#39; has been created
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -31,7 +31,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Workspace "bobby-workspace" deleted</title>
+    <title>Workspace &#34;bobby-workspace&#34; deleted</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -46,7 +46,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Workspace "bobby-workspace" deleted
+        Workspace &#34;bobby-workspace&#34; deleted
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -31,7 +31,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Workspace "bobby-workspace" deleted</title>
+    <title>Workspace &#34;bobby-workspace&#34; deleted</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -46,7 +46,7 @@ ication Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Workspace "bobby-workspace" deleted
+        Workspace &#34;bobby-workspace&#34; deleted
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -34,7 +34,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Workspace "bobby-workspace" marked as dormant</title>
+    <title>Workspace &#34;bobby-workspace&#34; marked as dormant</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -49,7 +49,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Workspace "bobby-workspace" marked as dormant
+        Workspace &#34;bobby-workspace&#34; marked as dormant
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -31,7 +31,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Workspace "bobby-workspace" marked as dormant</title>
+    <title>Workspace &#34;bobby-workspace&#34; marked as dormant</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -46,7 +46,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Workspace "bobby-workspace" marked as dormant
+        Workspace &#34;bobby-workspace&#34; marked as dormant
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -29,7 +29,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Workspace "bobby-workspace" manual build failed</title>
+    <title>Workspace &#34;bobby-workspace&#34; manual build failed</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -44,7 +44,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Workspace "bobby-workspace" manual build failed
+        Workspace &#34;bobby-workspace&#34; manual build failed
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -31,7 +31,8 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Workspace 'bobby-workspace' has been manually updated</title>
+    <title>Workspace &#39;bobby-workspace&#39; has been manually updated</t=
+itle>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -46,7 +47,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Workspace 'bobby-workspace' has been manually updated
+        Workspace &#39;bobby-workspace&#39; has been manually updated
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -31,7 +31,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Workspace "bobby-workspace" marked for deletion</title>
+    <title>Workspace &#34;bobby-workspace&#34; marked for deletion</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -46,7 +46,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Workspace "bobby-workspace" marked for deletion
+        Workspace &#34;bobby-workspace&#34; marked for deletion
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -27,7 +27,8 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Your workspace "bobby-workspace" is low on volume space</title>
+    <title>Your workspace &#34;bobby-workspace&#34; is low on volume space<=
+/title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -42,7 +43,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Your workspace "bobby-workspace" is low on volume space
+        Your workspace &#34;bobby-workspace&#34; is low on volume space
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -31,7 +31,8 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Your workspace "bobby-workspace" is low on volume space</title>
+    <title>Your workspace &#34;bobby-workspace&#34; is low on volume space<=
+/title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -46,7 +47,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Your workspace "bobby-workspace" is low on volume space
+        Your workspace &#34;bobby-workspace&#34; is low on volume space
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -28,7 +28,8 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Your workspace "bobby-workspace" is low on memory</title>
+    <title>Your workspace &#34;bobby-workspace&#34; is low on memory</title=
+>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -43,7 +44,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Your workspace "bobby-workspace" is low on memory
+        Your workspace &#34;bobby-workspace&#34; is low on memory
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -27,7 +27,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Your account "bobby" has been activated</title>
+    <title>Your account &#34;bobby&#34; has been activated</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -42,7 +42,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Your account "bobby" has been activated
+        Your account &#34;bobby&#34; has been activated
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -25,7 +25,7 @@ Content-Type: text/html; charset=UTF-8
    <meta charset=3D"UTF-8" />
    <meta name=3D"viewport" content=3D"width=3Ddevice-width, initial-scale=
 =3D1.0" />
-    <title>Your account "bobby" has been suspended</title>
+    <title>Your account &#34;bobby&#34; has been suspended</title>
  </head>
  <body style=3D"margin: 0; padding: 0; font-family: -apple-system, system-=
 ui, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarel=
@@ -40,7 +40,7 @@ er Logo" style=3D"height: 40px;" />
      </div>
      <h1 style=3D"text-align: center; font-size: 24px; font-weight: 400; m=
 argin: 8px 0 32px; line-height: 1.5;">
-        Your account "bobby" has been suspended
+        Your account &#34;bobby&#34; has been suspended
      </h1>
      <div style=3D"line-height: 1.5;">
        <p>Hi Bobby,</p>
@@ -114,10 +114,29 @@ func PlaintextFromMarkdown(markdown string) (string, error) {
 }

 func HTMLFromMarkdown(markdown string) string {
-	p := parser.NewWithExtensions(parser.CommonExtensions | parser.HardLineBreak) // Added HardLineBreak.
+	return renderHTMLFromMarkdown(markdown, parser.CommonExtensions|parser.HardLineBreak, html.CommonFlags|html.SkipHTML)
+}
+
+// HTMLFromMarkdownSafe renders Markdown to HTML with additional security
+// hardening for content that may include user-controlled values (e.g.
+// notification emails): autolinks are disabled so that only explicit Markdown
+// link syntax produces <a> tags, and Safelink drops links whose scheme is not
+// http/https/ftp/mailto.
+//
+// The hardening is scoped to this function. HTMLFromMarkdown renders
+// admin-authored deployment text (OIDCConfig.SignupsDisabledText) and keeps the
+// standard flags so links with custom schemes (e.g. slack://) still render.
+func HTMLFromMarkdownSafe(markdown string) string {
+	extensions := parser.CommonExtensions | parser.HardLineBreak
+	extensions &^= parser.Autolink
+	return renderHTMLFromMarkdown(markdown, extensions, html.CommonFlags|html.SkipHTML|html.Safelink)
+}
+
+func renderHTMLFromMarkdown(markdown string, extensions parser.Extensions, flags html.Flags) string {
+	p := parser.NewWithExtensions(extensions)
 	doc := p.Parse([]byte(markdown))
 	renderer := html.NewRenderer(html.RendererOptions{
-		Flags: html.CommonFlags | html.SkipHTML,
+		Flags: flags,
 	})
 	return string(bytes.TrimSpace(gomarkdown.Render(doc, renderer)))
 }
@@ -1,6 +1,7 @@
 package render_test

 import (
+	"strings"
 	"testing"

 	"github.com/stretchr/testify/require"
@@ -143,3 +144,114 @@ func TestInnerTextFromMarkdown(t *testing.T) {
 		})
 	}
 }
+
+func TestHTMLFromMarkdownSafe(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name     string
+		input    string
+		contains []string
+		absent   []string
+	}{
+		{
+			name:     "explicit https link preserved",
+			input:    "[Coder](https://coder.com)",
+			contains: []string{`<a href="https://coder.com">Coder</a>`},
+		},
+		{
+			name:     "explicit http link preserved",
+			input:    "[Link](http://example.com)",
+			contains: []string{`<a href="http://example.com">Link</a>`},
+		},
+		{
+			name:   "javascript URI blocked by Safelink",
+			input:  "[Click](javascript:alert(1))",
+			absent: []string{"javascript:", "<a href"},
+		},
+		{
+			name:   "data URI blocked by Safelink",
+			input:  "[Click](data:text/html,<script>alert(1)</script>)",
+			absent: []string{"data:", "<a href"},
+		},
+		{
+			name:     "bare URL NOT auto-linked",
+			input:    "Visit https://evil.example for details",
+			absent:   []string{"<a href"},
+			contains: []string{"https://evil.example"},
+		},
+		{
+			name:     "bold and emphasis still work",
+			input:    "**bold** and *italic*",
+			contains: []string{"<strong>bold</strong>", "<em>italic</em>"},
+		},
+		{
+			name:   "raw HTML stripped",
+			input:  `<script>alert(1)</script>`,
+			absent: []string{"<script>"},
+		},
+		{
+			name:     "escaped markdown renders as literal text",
+			input:    `\[not a link\]\(https://evil.example\)`,
+			absent:   []string{"<a href"},
+			contains: []string{"[not a link]"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			result := render.HTMLFromMarkdownSafe(tt.input)
+			for _, s := range tt.contains {
+				if !strings.Contains(result, s) {
+					t.Errorf("output %q should contain %q", result, s)
+				}
+			}
+			for _, s := range tt.absent {
+				if strings.Contains(result, s) {
+					t.Errorf("output %q should NOT contain %q", result, s)
+				}
+			}
+		})
+	}
+}
+
+func TestHTMLFromMarkdownSafelink(t *testing.T) {
+	t.Parallel()
+
+	// Safelink is scoped to HTMLFromMarkdownSafe. HTMLFromMarkdown renders
+	// admin-authored deployment text and keeps its pre-existing behavior, so
+	// it does not block or rewrite link schemes.
+	t.Run("HTMLFromMarkdownSafe blocks javascript URI", func(t *testing.T) {
+		t.Parallel()
+		result := render.HTMLFromMarkdownSafe("[Click](javascript:alert(1))")
+		if strings.Contains(result, "javascript:") {
+			t.Error("HTMLFromMarkdownSafe should block javascript: URIs via Safelink")
+		}
+	})
+
+	t.Run("HTMLFromMarkdown does not rewrite custom-scheme links", func(t *testing.T) {
+		t.Parallel()
+		// Admin-authored deployment text may legitimately use custom schemes.
+		result := render.HTMLFromMarkdown("[Open the app](slack://channel)")
+		if !strings.Contains(result, `href="slack://channel"`) {
+			t.Errorf("HTMLFromMarkdown should render custom-scheme links, got %q", result)
+		}
+	})
+
+	t.Run("HTMLFromMarkdown allows autolinks", func(t *testing.T) {
+		t.Parallel()
+		result := render.HTMLFromMarkdown("Visit https://coder.com for details")
+		if !strings.Contains(result, "<a href") {
+			t.Error("HTMLFromMarkdown should auto-link bare URLs")
+		}
+	})
+
+	t.Run("HTMLFromMarkdownSafe disables autolinks", func(t *testing.T) {
+		t.Parallel()
+		result := render.HTMLFromMarkdownSafe("Visit https://coder.com for details")
+		if strings.Contains(result, "<a href") {
+			t.Error("HTMLFromMarkdownSafe should NOT auto-link bare URLs")
+		}
+	})
+}