Mozilla yesterday patched 11 vulnerabilities, 10 of them critical, in Firefox 3.0, the browser that has another few months to live.

The update to Firefox 3.0.12 was the first since Mozilla launched the brand-new Firefox 3.5 at the end of June. As is its practice, Mozilla will discontinue support and stop security updates for the older edition approximately six months after the release of 3.5. It has set Firefox 3.0's "kill date" as sometime in January 2010.

Of the 11 flaws fixed in Firefox 3.0.12 -- the same number patched in the previous security update -- 10 were rated critical and one as "high" in Mozilla's four-step system. Danish bug tracker Secunia ranked the bunch as "highly critical," it's second-from-the-top tag.

Five of the 11 vulnerabilities are in the browser's rendering engine, a frequent target of Mozilla's patching. "Some of these crashes showed evidence of memory corruption under certain circumstances and we presume that with enough effort at least some of these could be exploited to run arbitrary code," said Mozilla in the accompanying advisory. It urged users to disable JavaScript if Firefox could not be immediately updated to 3.0.12.

Mozilla also patched critical vulnerabilities in Firefox's use of Adobe Flash, in open-source font-rendering libraries and in several other parts of the browser.

Eight of the 11 vulnerabilities patched Tuesday have already been addressed in the original version of Firefox 3.5, or the update to 3.5.1. that Mozilla rushed out last week to quash a zero-day bug.

It's not unheard of for Mozilla to patch one version of its browser while leaving another temporarily vulnerable. When the company has done that, it has patched the newest edition first, then backtracked to update the older version later, as it did in this case.

Mozilla plans to update Firefox 3.5 again -- later this month or early in August -- with the patches it had originally scheduled for 3.5.1. "[The] goal of this release should be a quick-turnaround [with] topcrash [and] security/stability patches," Mozilla said in notes published after a weekly status meeting.

Firefox 3.0.12 can be downloaded for Windows, Mac OS X and Linux, but current users can also call up their browser's built-in updater or wait for the automatic update notification, which should pop up in the next 48 hours.