Firefox 99 is out – no major bugs, but update anyway!


The once-every-four-weeks security update to Mozilla’s Firefox browser officially arrived today.

The regular version of Firefox is now 99.0while the Extended Support Release, which gets security fixes without any feature updates, is now 91.8.0 ESR.

Add together the first two numbers in the ESR release triplet and you should get the same value as the first number in the regular release.

(Thus, 91.8 ESR has the feature set of Firefox 91.0, plus the same 8 sets of four-weekly security patches that came out in the intervening full releases, thus aligning it security-wise with version (91 + 8) .0, ie 99.0.)

Fortunately, as in the April 2022 Google Android update we just wrote about that happened to arrive on the same day, there were no critical security fixes and no zero-day holes patched.

In particular, although Mozilla admits that some of the memory management bugs that were fixed in Firefox 99.0 might be exploitable “With enough effort”no working exploits are yet known.

And with no known exploits at all, clearly there are no known exploits that were already being used the Bad Guys, or zero-days as they’re called in the jargon.