Firefox fix restores broken browser extensions -- but not for everyone

Mozilla has begun automatically distributing a Firefox update to fix a problem that broke extensions for many browser users on Friday.

Extensions, also called add-ons, let you customize browsers to do things like block ad tracking or offer video playback speed controls. Mozilla requires they be digitally signed to improve security. The certificate Mozilla uses for that purpose expired, though, so Firefox started disabling extensions it no longer considered safe.

Mozilla advised people to wait for the update. "The fix will be automatically applied in the background within the next few hours," said Kev Needham, Mozilla's product manager for add-ons, in a blog post early Saturday morning. "No active steps need to be taken to make add-ons work again. In particular, please do not delete and/or re-install any add-ons as an attempt to fix the issue."

Unfortunately for Firefox users and Mozilla, the fix doesn't reach everyone. Mozilla is updating Firefox with an unusual mechanism, the studies feature for testing new features, and some people may have disabled that. The fix doesn't yet work for Firefox on Android or the slower-moving Extended Support Release (ESR) version of Firefox. And some people aren't getting the update, Mozilla said on Twitter on Saturday.