Since May 3, Firefox has been trying to repair a glitch that resulted in user add-ons being disabled and/or broken. In its second attempt to repair the browser, the company issued an update on May 5 that should give users access to their malfunctioning extensions.
After failing to renew a security certificate on May 3, Firefox browser extensions were either immediately disabled or completely broken. Uninstalling and reinstalling the extensions failed to correct the issue. On May 4, Firefox released updates to repair the problem, but some users didn't regain access to their ads-ons. May 5, another update was announced to get extensions "back up & running before Monday".
In fact, while disabled and broken extensions have been the main issue, some users have also had problems with search engines and language packs. The update made available May 5 will supposedly fix all these problems, though Firefox announced that "there are some issues we're still working on."
The security certificate that had expired – which requires ad-ons to be signed by the company to ensure extensions are safe – is actually built right into the browser, so when this expired, Firefox automatically disabled everything that it deemed "unsafe", aka unsigned.
to Firefox's VP of engineering Joe Hildebrand, "Hundreds of dedicated Mozillians worked over the weekend" to bring users access to their malfunctioning extensions." – AFP Relaxnews