add escaping of comment text in webhook default JSON template

backend/app/notify/webhook.go

@@ -3,6 +3,7 @@ package notify
 import (
 	"bytes"
 	"context"
+	"encoding/json"
 	"fmt"
 	"text/template"
 	"time"
@@ -12,7 +13,7 @@ import (
 )
 
 const (
-	webhookDefaultTemplate = `{"text": "{{.Text}}"}`
+	webhookDefaultTemplate = `{"text": {{.Text | escapeJSONString}}}`
 )
 
 // WebhookParams contain settings for webhook notifications
@@ -49,7 +50,7 @@ func NewWebhook(params WebhookParams) (*Webhook, error) {
 		params.Template = webhookDefaultTemplate
 	}
 
-	payloadTmpl, err := template.New("webhook").Parse(params.Template)
+	payloadTmpl, err := template.New("webhook").Funcs(template.FuncMap{"escapeJSONString": escapeJSONString}).Parse(params.Template)
 	if err != nil {
 		return nil, fmt.Errorf("unable to parse webhook template: %w", err)
 	}
@@ -82,3 +83,12 @@ func (w *Webhook) SendVerification(_ context.Context, _ VerificationRequest) err
 func (w *Webhook) String() string {
 	return fmt.Sprintf("%s to %s", w.Webhook.String(), w.url)
 }
+
+// escapeJSONString escapes string for JSON
+func escapeJSONString(s string) (string, error) {
+	b, err := json.Marshal(s)
+	if err != nil {
+		return "", err
+	}
+	return string(b), nil
+}

backend/app/notify/webhook_test.go

@@ -2,6 +2,9 @@ package notify
 
 import (
 	"context"
+	"io"
+	"net/http"
+	"net/http/httptest"
 	"testing"
 	"time"
 
@@ -34,6 +37,32 @@ func TestWebhook_NewWebhook(t *testing.T) {
 	assert.Contains(t, err.Error(), "unable to parse webhook template")
 }
 
+// https://github.com/umputun/remark42/issues/1791
+func TestWebhook_ReceiveValidJSON(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(_ http.ResponseWriter, r *http.Request) {
+		assert.Equal(t, r.URL.Path, "/webhook-notify")
+		assert.Equal(t, "POST", r.Method)
+		body, err := io.ReadAll(r.Body)
+		assert.NoError(t, err)
+		t.Log("received body", string(body))
+		assert.JSONEq(t, `{"text": "<p>testme</p>\n"}`, string(body))
+	}))
+	defer ts.Close()
+
+	wh, err := NewWebhook(WebhookParams{
+		URL:     ts.URL + "/webhook-notify",
+		Headers: []string{"Content-Type:application/json,text/plain"},
+	})
+	assert.NoError(t, err)
+	assert.NotNil(t, wh)
+
+	f := store.NewCommentFormatter()
+	c := store.Comment{Text: f.FormatText("testme", false), ParentID: "1", ID: "999"}
+
+	err = wh.Send(context.Background(), Request{Comment: c})
+	assert.NoError(t, err)
+}
+
 func TestWebhook_Send(t *testing.T) {
 	wh, err := NewWebhook(WebhookParams{
 		URL:     "bad-url",

site/src/docs/configuration/notifications/index.md

@@ -46,4 +46,4 @@ If all goes fine, you should be able to see the following message on your Slack
 
 You need to set `NOTIFY_ADMINS=webhook` to enable WebHook notifications on all new comments and set at least `NOTIFY_WEBHOOK_URL` for them to start working.
 
-Additionally, you might want to set `NOTIFY_WEBHOOK_TEMPLATE` (which is Go Template, `{"text": "{{.Text}}"}` by default) and `NOTIFY_WEBHOOK_HEADERS`, which is HTTP header(s) in format `Header1:Value1,Header2:Value2,...`.
+Additionally, you might want to set `NOTIFY_WEBHOOK_TEMPLATE` (which is Go Template, `{"text": {{.Text | escapeJSONString}}}` by default) and `NOTIFY_WEBHOOK_HEADERS`, which is HTTP header(s) in format `Header1:Value1,Header2:Value2,...`.