"A vulnerability has been reported in Mozilla and Mozilla Firefox, allowing malicious websites to spoof the user interface. The problem is that Mozilla and Mozilla Firefox don't restrict websites from including arbitrary, remote XUL (XML User Interface Language) files. This can be exploited to "hijack" most of the user interface (including tool bars, SSL certificate dialogs, address bar and more), thereby controlling almost anything the user sees.
The Mozilla user interface is built using XUL files. A PoC (Proof of Concept) exploit for Mozilla Firefox has been published. The PoC spoofs a SSL secured PayPal website. This has been confirmed using Mozilla 1.7 for Linux, Mozilla Firefox 0.9.1 for Linux, Mozilla 1.7.1 for Windows and Mozilla Firefox 0.9.2 for Windows. Prior versions may also be affected."
Mozilla bug# 244965