__Summary
Using javascript it is possible to spoof the content of security and download dialogs by partly covering them with a popup window. This can fool a user to download and automaticly execute a file (if a file extension association exists) or to grant a script local data access (if codebase principals are enabled).
__Expected Behavior
Modal dialogs should always be on top and it should not be possible to obfuscate their appearance.
__Proof-of-Concept
http://www.mikx.de/firespoofing/
The PoC is designed for Firefox 1.0 running in a maximized window.
Part 1 - download dialog spoofing
Shows how to cover a download dialog and fool the user to execute a file with a standard windows file association (in this case a .ht file). BTW, remember the latest .ht buffer overflow...
Part 2 - security dialog spoofing
Shows how to cover a security dialog. Make sure codebase principals are enabled (not default but encouraged by many XUL sites). Creates the file c:\booom.txt to proof local system access.
__Status
The bug is confirmed but currently unfixed (open for more than 3 months). As a partial workaround set dom.disable_window_flip to true in about:config. The vendor failed to respond to multiple status requests which led to this public disclosure.
2004-09-20 Vendor informed (bugzilla.mozilla.org #260560) 2004-09-20 Vendor confirmed bug 2004-10-20 Status request (open for 1 month - no reply) 2005-01-03 Status request (open for 3 months - no reply) 2005-01-07 Status request (disclosure warning - no reply) 2005-01-11 Public disclosure
__Affected Software
Tested with Firefox 1.0, Mozilla 1.7.5 and Netscape 7.1 on Windows XP SP2.
__Contact Informations
Michael Krax <mikx@xxxxxxx> http://www.mikx.de/?p=7
mikx
