For those of you that haven't yet made the move to Firefox 3.0, the Mozilla folks have released Firefox 2.0.0.15 which according to the release notes link (see below) fixes a security vulnerability.  However, the "known vulnerabilities" page (linked from the release notes page) doesn't include any info (yet) on what that security fix is.

References:

http://www.mozilla.com/en-US/firefox/2.0.0.15/releasenotes/

http://www.mozilla.org/projects/security/known-vulnerabilities.html#firefox2.0.0.15

Update: (2008-07-02-14:15 UTC) Well, they have updated the known vulnerabilities page.  This version apparently fixes 12 issues, 4 of them critical, so if you are still running FF2, you'll want to update ASAP.  Also, note that Seamonkey was also updated to version 1.1.10 and included fixes for the same issues plus one additional critical vulnerability, so updated that one, too, if you use it.