We rolled-out a fix for release, beta and nightly users on Desktop. The fix will be automatically applied in the background within the next few hours, you don’t need to take active steps.

In order to be able to provide this fix on short notice, we are using the Studies system. You can check if you have studies enabled by going to Firefox Preferences -> Privacy & Security -> Allow Firefox to install and run studies.

You can disable studies again after your add-ons have been re-enabled.

Please do not delete your add-ons as an attempt to fix. You will lose any data related to the add-on. Disabled add-ons will not lose any data.

There is no fix available for Android at this time. The team is working on it.

We are working on a general fix that doesn’t need to rely on this and will keep you updated.

Hi Destrian, it's not malicious. An SSL certificate expired.

People have been working on fixing this and helping users with questions for the past 18 hours, and work is ongoing.

Here's the current support article on how to get the patch(es): Add-ons disabled or fail to install on Firefox.

If you are a Reddit user, check out https://www.reddit.com/r/firefox/ for lively discussion of the problem and various workarounds.

So, you all said... "a few hours..." Well, its been a bit longer than that. Whatever error you all had, killed off all but one plug in including Kaspersky... (not to mention NoScript, which is my real worry). Your comments to me say I have nothing more to do (other than enable studies, which I've done). When does this get fixed. Also- who's responsible? This is not the fault of the extensions/plug in guys...It's Mozilla/Firefoxes... I hope your taking appropriate action. This is simply unacceptable.

Hi Destrian, did you get the studies related to this fix, or did they never show up on the about:studies page?

If you got the studies, check whether the certificate was added. That would be on the Options/Preferences page:

• Windows: "3-bar" menu button (or Tools menu) > Options
• Mac: "3-bar" menu button (or Firefox menu) > Preferences
• Linux: "3-bar" menu button (or Edit menu) > Preferences
• Any system: type or paste about:preferences into the address bar and press Enter/Return to load it

In the search box at the top of the page, type cert and Firefox should filter to the Certificates section. Then click the "View Certificates" button. Check the "Authorities" tab to see whether Mozilla is listed with the new certificate. You can compare the attached screenshot.

If you got not studies and no certificate, try the manual method listed in this reply and/or the ones that follow: https://support.mozilla.org/questions/1258208#answer-1218876