The Internet is everywhere and just today we got the proof that even our browser packed with plugins just needs a working backbone. What has happened? Many of us may have realized that suddenly our beloved Firefox-plugins apparently ceased to exist, piece by piece. No changes have been made but plugins were deactivated. The reason? Expressed in a simple way, "just" an intermediate certificate expired...
What sounds quite eerie, having such an impact, is indeed the true story. An intermediate signing certificate, which was quite important for all Add-Ons, gently died - and wasn't renewed before this happened. Without any user interference your beloved browser and the plugins therein were simply laid to rest without an official chance of putting them on duty again.
With the certificate expired all affected add-ons were categorized as "dangerous" legacy add-ons as there is no signing process anymore - for now. The sad certificate was due to renewal some weeks ago and nobody knows why it hasn't been renewed so far. The Mozilla Foundation, creator and maintainer of Firefox, has already statedto work on a proper fix. Even Mozilla's official bug tracker has his entry for this issue which is defined as Bug 1548973.
For now, there is only one workaround that works, but cannot be recommended as it handles how add-ons are being handled and signed. Just enter "about:config" in the address bar and search for the term "xpinstall.signatures.required". Double-click this entry should switch the value "true" to "false". Of course this is just a temporary fix so be sure to switch this value back once Mozilla has solved this issue!
Last but not least we see how much impact such an error can have on our work with a "simple" browser and its add-ons. Quite frightening but surely this is the darker side of the same coin: The Internet is everywhere and a malfunction causing a certificate to expire simply harms your local browser - sounds easy although it is strange. In this case, a security component (certificate) which handles third-party add-ons took care of deactivating all those plugins that make your browser what is is.
Phew - just let's hope that Mozilla will fix this very soon and don't forget to toggle the parameter stated above back to "true" once you choose to use the workaround!
Edit: The issue has been fixed with the releaseof Firefox 66.0.4: