1 files changed, 14 insertions, 6 deletions

diff --git a/ext/web/02_event.js b/ext/web/02_event.js
index 9d5169b9e..f5b4bd7d3 100644
--- a/ext/web/02_event.js
+++ b/ext/web/02_event.js
@@ -917,6 +917,7 @@
   class EventTarget {
     constructor() {
       this[eventTargetData] = getDefaultTargetData();
+      this[webidl.brand] = webidl.brand;
     }
 
     addEventListener(
@@ -924,6 +925,8 @@
       callback,
       options,
     ) {
+      const self = this ?? globalThis;
+      webidl.assertBranded(self, EventTargetPrototype);
       const prefix = "Failed to execute 'addEventListener' on 'EventTarget'";
 
       webidl.requiredArguments(arguments.length, 2, {
@@ -939,7 +942,7 @@
         return;
       }
 
-      const { listeners } = (this ?? globalThis)[eventTargetData];
+      const { listeners } = self[eventTargetData];
 
       if (!(ReflectHas(listeners, type))) {
         listeners[type] = [];
@@ -965,7 +968,7 @@
           // If listener’s signal is not null, then add the following abort
           // abort steps to it: Remove an event listener.
           signal.addEventListener("abort", () => {
-            this.removeEventListener(type, callback, options);
+            self.removeEventListener(type, callback, options);
           });
         }
       }
@@ -978,11 +981,13 @@
       callback,
       options,
     ) {
+      const self = this ?? globalThis;
+      webidl.assertBranded(self, EventTargetPrototype);
       webidl.requiredArguments(arguments.length, 2, {
         prefix: "Failed to execute 'removeEventListener' on 'EventTarget'",
       });
 
-      const { listeners } = (this ?? globalThis)[eventTargetData];
+      const { listeners } = self[eventTargetData];
       if (callback !== null && ReflectHas(listeners, type)) {
         listeners[type] = ArrayPrototypeFilter(
           listeners[type],
@@ -1010,14 +1015,15 @@
     }
 
     dispatchEvent(event) {
-      webidl.requiredArguments(arguments.length, 1, {
-        prefix: "Failed to execute 'dispatchEvent' on 'EventTarget'",
-      });
       // If `this` is not present, then fallback to global scope. We don't use
       // `globalThis` directly here, because it could be deleted by user.
       // Instead use saved reference to global scope when the script was
       // executed.
       const self = this ?? window;
+      webidl.assertBranded(self, EventTargetPrototype);
+      webidl.requiredArguments(arguments.length, 1, {
+        prefix: "Failed to execute 'dispatchEvent' on 'EventTarget'",
+      });
 
       const { listeners } = self[eventTargetData];
       if (!ReflectHas(listeners, event.type)) {
@@ -1042,6 +1048,7 @@
   }
 
   webidl.configurePrototype(EventTarget);
+  const EventTargetPrototype = EventTarget.prototype;
 
   defineEnumerableProps(EventTarget, [
     "addEventListener",
@@ -1411,6 +1418,7 @@
     reportException(error);
   }
 
+  window[webidl.brand] = webidl.brand;
   window.Event = Event;
   window.EventTarget = EventTarget;
   window.ErrorEvent = ErrorEvent;