Firefox 2.0.0.14 has been released and is currently available through the automatic update function in Firefox and the main Mozilla website. The new update to Firefox 2 is a security update that fixes one critical issue, a crash in the JavaScript garbage collector which is actually more of a stability fix than a security fix. The reason why it is still
listed as a security fix is that issues like these have been exploited before in the past.
I suggest you update your version of Firefox 2 as soon as possible, users of Firefox 3 seem safe for now and do not have to do anything. The same issue will also be fixed in upcoming releases of Thunderbird and Seamonkey which are not yet available for download.
Firefox 2.0.0.14 critical update