1 files changed, 35 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/browsers/the-windowproxy-exotic-object/windowproxy-prototype-setting-goes-cross-origin-domain.sub.html b/testing/web-platform/tests/html/browsers/the-windowproxy-exotic-object/windowproxy-prototype-setting-goes-cross-origin-domain.sub.html
new file mode 100644
index 0000000000..c2a6def6c2
--- /dev/null
+++ b/testing/web-platform/tests/html/browsers/the-windowproxy-exotic-object/windowproxy-prototype-setting-goes-cross-origin-domain.sub.html
@@ -0,0 +1,35 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>[[SetPrototypeOf]] on a WindowProxy object should not allow changing its value: cross-origin via document.domain after initially getting the object</title>
+<link rel="help" href="http://html.spec.whatwg.org/multipage/#windowproxy-setprototypeof">
+<link rel="author" title="Domenic Denicola" href="mailto:d@domenic.me">
+
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/test-setting-immutable-prototype.js"></script>
+
+<iframe src="/common/blank.html"></iframe>
+
+<script>
+"use strict";
+window.onload = () => {
+  const target = frames[0];
+  const origProto = Object.getPrototypeOf(target);
+
+  test(() => {
+    assert_not_equals(origProto, null);
+  }, "Same-origin (for now): the prototype is accessible");
+
+  document.domain = "{{host}}";
+
+  test(() => {
+    assert_equals(Object.getPrototypeOf(target), null);
+  }, "Became cross-origin via document.domain: the prototype is now null");
+
+  testSettingImmutablePrototype("Became cross-origin via document.domain", target, null, { isSameOriginDomain: false });
+
+  testSettingImmutablePrototypeToNewValueOnly(
+    "Became cross-origin via document.domain", target, origProto,
+    "the original value from before going cross-origin", { isSameOriginDomain: false });
+};
+</script>