Secunia

A weakness has been identified in Mozilla, which can be exploited by malicious people to manipulate information displayed in the status bar.

It is possible to manipulate information displayed in the status bar by including the URL encoded representation "%00" in a link. Since this can be done without using any script code, disabling the script setting "Change status bar text" will not prevent this.

This can be exploited to trick users, who have disabled script manipulation of the status bar and therefore trust information displayed in it.

A test is available at:
http://secunia.com/internet_explorer_address_bar_spoofing_test/

The weakness has been confirmed in Mozilla 1.0.2 for Linux and 1.5 for Windows. Other versions may also be affected.

NOTE: This issue is not the same as the Internet Explorer URL (Address Bar) Spoofing Vulnerability:
SA10395

Solution
The issue has been fixed in the 1.6 branch and the forthcoming version 1.4.2.
Further details available in Customer Area

Other references
Further details available in Customer Area

Deep Links
Links available in Customer Area