Mozilla has plugged a critical unpatched cross-platform vulnerability in Firefox a week ahead of its previously announced schedule.
Firefox 3.6.2 fixes a flaw first discovered by security researcher Evgeny Legerov last month, and confirmed by Mozilla last week.
The zero-day vulnerability - now identified as an integer overflow flaw involving the WOFF font decoder used by the latest version of Firefox - created a means for hackers to distribute malware via drive by download attacks from maliciously constructed sites, providing vulnerable marks were using Firefox version 3.6. Early versions of the open source browser do not use the vulnerable WOFF decoder technology, and are therefore immune from the bug.
Exploit code was available though not in the "weaponised" form beloved by script kiddies - instead the exploit was available as an add-on to the Immunity Canvas automated exploitation system.
Mozilla originally promised an update on 30 March in an advisory last Thursday, offering a beta version of Firefox 3.6.2 as an alternative for those disinclined to wait it out. That wasn't good enough for the German government's BürgerCERT security response team, which advised users on Monday to avoid Firefox 3.6 until a fix was available.
Possibly prompted by this slap in the chops, Mozilla released a full version of the latest version of the browser on Monday night. An absence of problems related to the beta version of 3.6.2 in the four days since its release cleared the passage for the release of the update to the open source browser.
Release notes for Firefox 3.6.2 can be found on Mozilla's website here. ®