fix: sanitize payment response NUL bytes

backend/internal/service/payment_order.go

@@ -453,6 +453,7 @@ func (s *PaymentService) invokeProvider(ctx context.Context, order *dbent.Paymen
 		}
 		return nil, classifyCreatePaymentError(req, sel.ProviderKey, err)
 	}
+	sanitizeCreatePaymentResponseDetails(pr)
 	_, err = s.entClient.PaymentOrder.UpdateOneID(order.ID).
 		SetNillablePaymentTradeNo(psNilIfEmpty(pr.TradeNo)).
 		SetNillablePayURL(psNilIfEmpty(pr.PayURL)).
@@ -480,6 +481,22 @@ func (s *PaymentService) invokeProvider(ctx context.Context, order *dbent.Paymen
 	return resp, nil
 }
 
+func sanitizeCreatePaymentResponseDetails(pr *payment.CreatePaymentResponse) {
+	if pr == nil {
+		return
+	}
+	pr.TradeNo = removePostgresTextNUL(pr.TradeNo)
+	pr.PayURL = removePostgresTextNUL(pr.PayURL)
+	pr.QRCode = removePostgresTextNUL(pr.QRCode)
+}
+
+func removePostgresTextNUL(value string) string {
+	if !strings.ContainsRune(value, 0) {
+		return value
+	}
+	return strings.ReplaceAll(value, "\x00", "")
+}
+
 func buildProviderCreatePaymentRequest(req CreateOrderRequest, sel *payment.InstanceSelection, orderID, amount, subject string) payment.CreatePaymentRequest {
 	return payment.CreatePaymentRequest{
 		OrderID:            orderID,

backend/internal/service/payment_order_result_test.go

@@ -91,6 +91,41 @@ func TestBuildCreateOrderResponseCopiesJSAPIPayload(t *testing.T) {
 	}
 }
 
+func TestSanitizeCreatePaymentResponseDetailsRemovesNULBytes(t *testing.T) {
+	t.Parallel()
+
+	resp := &payment.CreatePaymentResponse{
+		TradeNo:      "trade\x00-no",
+		PayURL:       "https://pay.example.com/\x00checkout",
+		QRCode:       "wxp://payment-token\x00",
+		ClientSecret: "secret\x00unchanged",
+	}
+
+	sanitizeCreatePaymentResponseDetails(resp)
+
+	if strings.ContainsRune(resp.TradeNo, 0) {
+		t.Fatalf("trade_no still contains NUL: %q", resp.TradeNo)
+	}
+	if strings.ContainsRune(resp.PayURL, 0) {
+		t.Fatalf("pay_url still contains NUL: %q", resp.PayURL)
+	}
+	if strings.ContainsRune(resp.QRCode, 0) {
+		t.Fatalf("qr_code still contains NUL: %q", resp.QRCode)
+	}
+	if resp.TradeNo != "trade-no" {
+		t.Fatalf("trade_no = %q, want trade-no", resp.TradeNo)
+	}
+	if resp.PayURL != "https://pay.example.com/checkout" {
+		t.Fatalf("pay_url = %q, want sanitized URL", resp.PayURL)
+	}
+	if resp.QRCode != "wxp://payment-token" {
+		t.Fatalf("qr_code = %q, want sanitized QR code", resp.QRCode)
+	}
+	if resp.ClientSecret != "secret\x00unchanged" {
+		t.Fatalf("client_secret = %q, should not be touched by payment detail sanitization", resp.ClientSecret)
+	}
+}
+
 func TestValidateSelectedCreateOrderAmountCurrencyRejectsFractionalZeroDecimal(t *testing.T) {
 	t.Parallel()