fix: Fixed a possible config-specific bypass via "is" attributes, thanks @Yaniv-git

Author: cure53

dist/purify.cjs.js

@@ -777,8 +777,8 @@ function createDOMPurify() {
       });
     }
     element.removeAttribute(name);
-    // We void attribute values for unremovable "is"" attributes
-    if (name === 'is' && !ALLOWED_ATTR[name]) {
+    // We void attribute values for unremovable "is" attributes
+    if (name === 'is') {
       if (RETURN_DOM || RETURN_DOM_FRAGMENT) {
         try {
           _forceRemove(element);