Extensions, which are called add-ons in Firefox, require digital signatures to improve browser security.
However, the certificate used by Mozilla to do this expired on Friday – resulting in Firefox automatically disabling certain extensions that it considered unsafe.
The company launched a fix on Saturday that used the Firefox "studies tool", which is used for testing new features, but users who have disabled this feature did not receive the fix.
As a result, Mozilla released a more traditional fix on Sunday that directly repaired the issue with the certificate, which works on PCs, Android, and the ESR version of the browser.
"No active steps need to be taken to make add-ons work again. In particular, please do not delete and/or reinstall any add-ons as an attempt to fix the issue," said Mozilla product manager for add-ons Kev Needham in a blog post.