Fix XSS in cookie banner translation rendering

Validate translation string values server-side with NoHTML() and
MaxLen(2000) to reject HTML in the translations JSON blob. On the
client side, escape user-provided template text before innerHTML
injection in banner_description and placeholder_text paths.

Signed-off-by: Émile Ré <emile@getprobo.com>

packages/cookie-banner/src/activation.ts

@@ -13,7 +13,6 @@
 // PERFORMANCE OF THIS SOFTWARE.
 
 import type { BannerTexts } from "./i18n";
-import { interpolate } from "./i18n";
 import { removeCookies } from "./cookie-utils";
 import { LOCK_ICON } from "./html";
 
@@ -155,9 +154,13 @@ function createPlaceholder(
     }
   }
 
-  const phText = texts?.placeholder_text
+  let phText: string;
-    ? interpolate(texts.placeholder_text, { category: escapeHtml(displayLabel) })
+  if (texts?.placeholder_text) {
-    : `This content requires <strong>${escapeHtml(displayLabel)}</strong> cookies.`;
+    const parts = texts.placeholder_text.split("{{category}}");
+    phText = parts.map(p => escapeHtml(p)).join(`<strong>${escapeHtml(displayLabel)}</strong>`);
+  } else {
+    phText = `This content requires <strong>${escapeHtml(displayLabel)}</strong> cookies.`;
+  }
   const phButton = texts?.placeholder_button ?? "Manage cookie preferences";
 
   placeholder.innerHTML = [

packages/cookie-banner/src/themed-banner/themed-banner.ts

@@ -179,7 +179,8 @@ export class ProboThemedBanner extends HTMLElement {
           const linkText = this.esc(texts.privacy_policy_link_text ?? "Privacy Policy");
           link = `<a href="${this.esc(config.privacy_policy_url)}" target="_blank" rel="noopener noreferrer">${linkText}</a>`;
         }
-        el.innerHTML = interpolate(raw, { privacy_policy_link: link });
+        const parts = raw.split("{{privacy_policy_link}}");
+        el.innerHTML = parts.map(p => this.esc(p)).join(link);
       } else if (key === "panel_description") {
         el.textContent = interpolate(raw, { necessary_category: necessaryCategoryName });
       } else {

pkg/cookiebanner/service.go

@@ -276,6 +276,38 @@ func (r *UpsertCookieBannerTranslationRequest) Validate() error {
 	v.Check(r.CookieBannerID, "cookie_banner_id", validator.Required(), validator.GID(coredata.CookieBannerEntityType))
 	v.Check(r.Language, "language", validator.Required(), validator.SafeTextNoNewLine(10))
 
+	var flat map[string]json.RawMessage
+	if err := json.Unmarshal(r.Translations, &flat); err != nil {
+		v.Check("", "translations", validator.Required())
+		return v.Error()
+	}
+
+	for key, raw := range flat {
+		if key == "categories" {
+			var cats map[string]json.RawMessage
+			if json.Unmarshal(raw, &cats) == nil {
+				for catID, catRaw := range cats {
+					var catFields map[string]json.RawMessage
+					if json.Unmarshal(catRaw, &catFields) == nil {
+						for field, fieldRaw := range catFields {
+							var s string
+							if json.Unmarshal(fieldRaw, &s) == nil {
+								v.Check(s, fmt.Sprintf("translations.categories.%s.%s", catID, field), validator.NoHTML(), validator.MaxLen(2000))
+							}
+						}
+					}
+				}
+			}
+			continue
+		}
+
+		var s string
+		if json.Unmarshal(raw, &s) != nil {
+			continue
+		}
+		v.Check(s, "translations."+key, validator.NoHTML(), validator.MaxLen(2000))
+	}
+
 	return v.Error()
 }