Firefox (FF) users should be aware of a use-after-free vulnerability affecting Firefox versions 3.6.11 and earlier. The security team at Firefox has been working on getting a patch out since at least early Tuesday morning, delivering a v3.6.12 release candidate available for brave nightly build developers and testers last night.
A zero day exploit attacking this vulnerability was used at the compromised Nobel Peace Prize website to drop a trojan on unsuspecting visitors’ systems, although the 0day was limited in that it did not implement well known ROP or JOP techniques (link to zipped pdf of VB2010 presentation slides) to effectively attack defensive technologies on newer Windows Vista and 7 platforms like DEP and ASLR. It effectively attacked newer FF on older versions of Windows.
UPDATE: Mozilla Firefox build 3.6.12 is out! In Firefox 3.6.11, you can click Help -> Check for updates… It includes the patch for msfa2010-73, “Heap buffer overflow mixing document.write and DOM insertion”, a problem otherwise described as the previously posted “use after free”. Readers interested in technical details of the vulnerability should check out the bug link previously posted above, the report “Interleaving document.write and appendChild can lead to duplicate text frames and overrunning of text run buffers” is now open to the public. Updating Firefox v3.6.11 takes under a minute, but requires a Firefox restart. The browser makes a best effort to restore any tabs that you may have had open at time of restart.