Firefox 66.0.4 Released with Disabled Ad-dons Fix

Update: Mozilla released version 66.0.4, including fix for expired certificate and disabled addons. You can use or download Firefox's automatic update feature here. To reflect this, this article has been updated.

Mozilla Firefox 66.0.4 was released on the Stable channel and contains a fix for the expired intermediate signing certificate that disabled all ad-dons on Friday.

On Friday, Mozilla allowed the expiry of an intermediate certificate used to sign addons from Firefox. Since Firefox requires addons to be signed by a valid certificate, users suddenly disabled all of their Firefox ad-dons once the certificate expired.

As a temporary fix, Mozilla issued a new intermediate signing certificate through its Normandy Study system. Once the hotfix has been installed, addons will be enabled again automatically.

You need to enable the Study system to use this system. However, doing so provides Mozilla with telemetry about how you use Firefox and some consider this a risk to privacy.

Even with the studies enabled, some users, including myself, report that they do not receive the hotfix.

Version 66.0.4 fixes expired certificate without studies

Mozilla has released Firefox 66.0.4 now, which includes a new intermediate signing certificate that has not expired and will force re-verification of the signature.


Three release candidates of Firefox 66.0.4 have been created over the past 2 days to fix this bug, with the first one being pulled as it did not properly resolve the ad-don problems. The third release candidate was the last candidate built before Mozilla released it to the public.

Firefox 66.0.4 Release

Mozilla's release notes for 66.0.4 have been updated to include the following fix as part of the change list.

Repaired certificate chain to re-enable web extensions that had been disabled

Firefox 66.0.4 Release Notes

Users should expect to see auto-update pushing Mozilla Firefox 66.0.4 as we speak.