CONSOLE MESSAGE: line 1: SecurityError: Blocked a frame with origin "http://127.0.0.1:8000" from accessing a cross-origin frame. Protocols, domains, and ports must match.
This page opens a window to "", injects malicious code, and then navigates its opener to the victim. The opened window then tries to scripts its opener after reloading itself as a javascript URL.
Code injected into window:
<script>window.location = 'javascript:\'<script>function write(target, message) { target.document.body.innerHTML = message; }setTimeout(function() {write(window.opener, \\\'FAIL: XSS was allowed.\\\');}, 100);setTimeout(function() {write(window.opener.top.frames[1], \\\'SUCCESS: Window remained in original SecurityOrigin.\\\');}, 200);setTimeout(function() { if (window.testRunner) testRunner.globalFlag = true; }, 300);<\\\/script>\''</script>
 

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Frame: '<!--frame1-->'
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This page doesn't do anything special (except signal that it has finished loading).

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Frame: '<!--frame2-->'
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SUCCESS: Window remained in original SecurityOrigin.