When the new page is loading, FrameLoader::clear is called to clear the old document and window.

Here's a snippet of FrameLoader::clear.

void FrameLoader::clear(Document* newDocument, bool clearWindowProperties, bool clearScriptObjects, bool clearFrameView)
{
    ...
    // Do this after detaching the document so that the unload event works.
    if (clearWindowProperties) {
        InspectorInstrumentation::frameWindowDiscarded(m_frame, m_frame.document()->domWindow());
        m_frame.document()->domWindow()->resetUnlessSuspendedForDocumentSuspension();
        m_frame.script().clearWindowShell(newDocument->domWindow(), m_frame.document()->pageCacheState() == Document::AboutToEnterPageCache); <<-------- (1)

        if (shouldClearWindowName(m_frame, *newDocument))
            m_frame.tree().setName(nullAtom);
    }

    ...
    m_frame.setDocument(nullptr); <<-------- (2)
    ...
}

The new document's window is attached at (1) before calling |m_frame.setDocument(nullptr)| that calls unload event handlers. So in the unload event handler, we could execute arbitrary javascript code on new document's window with a javascript: URI.


Tested on Safari 10.0.2(12602.3.12.0.1).


This bug is subject to a 90 day disclosure deadline. If 90 days elapse
without a broadly available patch, then the bug report will automatically
become visible to the public.

 

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