diff --git a/testing/web-platform/meta/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.html.ini b/testing/web-platform/meta/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.html.ini
new file mode 100644
index 0000000000000..3cfe72343b156
--- /dev/null
+++ b/testing/web-platform/meta/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.html.ini
@@ -0,0 +1,282 @@
+[TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.html]
+  [getAttributeType("dummy", "onabort", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onauxclick", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onbeforeinput", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onbeforematch", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onbeforetoggle", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onblur", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "oncancel", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "oncanplay", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "oncanplaythrough", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onchange", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onclick", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onclose", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "oncontextlost", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "oncontextmenu", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "oncontextrestored", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "oncopy", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "oncuechange", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "oncut", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "ondblclick", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "ondrag", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "ondragend", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "ondragenter", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "ondragleave", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "ondragover", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "ondragstart", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "ondrop", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "ondurationchange", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onemptied", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onended", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onerror", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onfocus", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onformdata", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "oninput", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "oninvalid", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onkeydown", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onkeypress", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onkeyup", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onload", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onloadeddata", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onloadedmetadata", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onloadstart", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onmousedown", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onmouseenter", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onmouseleave", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onmousemove", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onmouseout", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onmouseover", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onmouseup", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onpaste", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onpause", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onplay", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onplaying", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onprogress", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onratechange", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onreset", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onresize", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onscroll", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onscrollend", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onsecuritypolicyviolation", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onseeked", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onseeking", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onselect", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onslotchange", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onstalled", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onsubmit", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onsuspend", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "ontimeupdate", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "ontoggle", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onvolumechange", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onwaiting", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onwheel", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onafterprint", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onbeforeprint", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onbeforeunload", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onhashchange", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onlanguagechange", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onmessage", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onmessageerror", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onoffline", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "ononline", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onpagehide", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onpagereveal", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onpageshow", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onpageswap", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onpopstate", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onrejectionhandled", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onstorage", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onunhandledrejection", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onunload", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onencrypted", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onwaitingforkey", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onbegin", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onend", "dummyNs", attrNs)]
+    expected: FAIL
+
+  [getAttributeType("dummy", "onrepeat", "dummyNs", attrNs)]
+    expected: FAIL
diff --git a/testing/web-platform/tests/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.html b/testing/web-platform/tests/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.html
new file mode 100644
index 0000000000000..efdcf265622fb
--- /dev/null
+++ b/testing/web-platform/tests/trusted-types/TrustedTypePolicyFactory-getAttributeType-event-handler-content-attributes.tentative.html
@@ -0,0 +1,48 @@
+<!DOCTYPE html>
+<link rel="help" href="https://w3c.github.io/trusted-types/dist/spec/#dom-trustedtypepolicyfactory-getattributetype">
+<link rel="help" href="https://w3c.github.io/trusted-types/dist/spec/#abstract-opdef-get-trusted-type-data-for-attribute">
+<link rel="help" href="https://github.com/w3c/trusted-types/issues/520">
+<meta name="assert" content="getAttributeType() with empty attributeNs returns 'TrustedScript' for event handler content attributes.">
+<meta name="timeout" content="long">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/resources/WebIDLParser.js"></script>
+<script src="support/namespaces.js"></script>
+<script>
+promise_setup(async function() {
+  let attributeNames = [];
+  function addOnAttributes(IDL, interfaceName) {
+    // Parsing the whole IDL file is slow, so use a small regexp to extract only
+    // the part that is relevant for this test.
+    let regexp = new RegExp(`^.*\(partial \)?interface \(mixin \)?${interfaceName}[^{]*{[^{}]*};$`, "m");
+    let parsedIDL = WebIDL2.parse(IDL.match(regexp)[0]);
+    parsedIDL.find(idl => idl.name === interfaceName)
+      .members.map(member => member.name)
+      .filter(name => name.length >= 3 && name.startsWith("on") &&
+              !name.startsWith("onwebkit"))
+      .forEach(name => attributeNames.push(name));
+  }
+
+  const htmlIDL = await (await fetch("/interfaces/html.idl")).text();
+  ["GlobalEventHandlers", "WindowEventHandlers"].forEach(interfaceName => {
+    addOnAttributes(htmlIDL, interfaceName);
+  });
+
+  const entrypedMediaIDL = await (await fetch("/interfaces/encrypted-media.idl")).text();
+  addOnAttributes(entrypedMediaIDL, "HTMLMediaElement");
+
+  const svgAnimationsIDL = await (await fetch("/interfaces/svg-animations.idl")).text();
+  addOnAttributes(svgAnimationsIDL, "SVGAnimationElement");
+
+  for (const attributeName of attributeNames) {
+    promise_test(async () => {
+      NSURI_ARRAY.forEach(attrNs => {
+        assert_equals(trustedTypes.getAttributeType(
+          "dummy", attributeName, "dummyNs", attrNs),
+          attrNs === NSURI_EMPTY ? "TrustedScript" : null,
+          `for attrNs='${attrNs}'`);
+      });
+    }, `getAttributeType("dummy", "${attributeName}", "dummyNs", attrNs)`);
+  }
+});
+</script>