Sorry, the Add-ons team is working on a fix for this. It looks like a certificate used to sign many popular extensions expired. The verification process checks that certificate, and anything that doesn't pass is blocked.

I don't know how soon re-signed versions of those extensions will become available, or whether another workaround will be discovered. We are all hoping to learn more soon.

Thanks for the update.

If the certificate became invalid, the add-on should be taken off the website, or a proper error message should popup at the very least, to avoid confusion.

Thanks for the reply. I am currently using an alternate browser until Firefox sorts this, because according to the top response it looks like this may take ages to fix.

so when the team fix the problem, will everything be rollback and i can use the addons just as used to?

Hi Ajay-ajay, we don't know yet.

Official updates are expected to be posted here:

https://discourse.mozilla.org/t/certificate-issue-causing-add-ons-to-be-disabled-or-fail-to-install/39047

Currently, the only workaround is to set your system clock back (for example, if your date is May 3, set to May 2; if your date is May 4, set to May 3). You might have to reinstall extensions after that, or maybe Firefox will detect the difference at your next shut down/restart. Changing the date may have other consequences, so I understand this option isn't ideal.

Forum volunteers will be around to update these threads when we have something useful to add, so if you have email notification on, you should get that.

Mozilla has rolled-out a fix for this. 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, they are using the Studies system. You can check if you have studies enabled

1. Go to [=] > Options > Privacy & Security.
2. Make sure Allow Firefox to install and run studies is check marked.

I you had it disabled, you can disable studies again after your add-ons have been re-enabled.

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

"Allow Firefox to install and run studies" was already checked for me, and it isn't making any difference at all. It's now late afternoon and this issue still is not resolved, and it doesn't appear that it will be any time soon. You mentioned a fix being rolled out hrs. ago, but I still have no ability to use add ons of any kind. No themes, no ad blocker, etc. I'm using an alternate browser and would suggest to anyone else who sees this thread to do likewise.

See also:

• https://support.mozilla.org/en-US/kb/add-ons-disabled-or-fail-to-install-firefox
• https://blog.mozilla.org/addons/2019/05/04/update-regarding-add-ons-in-firefox/

You can temporarily set app.normandy.run_interval_seconds to a lower value (21600 => 100) to see whether that gives the hotfix. Close and restart Firefox and check about:studies.

• hotfix-update-xpi-signing-intermediate-bug-1548973
• hotfix-reset-xpi-verification-timestamp-1548973

You may have to refresh the about:studies page a few times.

Do NOT forget to reset app.normandy.run_interval_seconds when about:studies shows that the hotfix has been applied.

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• http://kb.mozillazine.org/about:config

Add ons seemed to be restored now, and I didn't do anything, so I'll mark this issue closed and hope that the suggestions here helped other people. As for myself it just restored on it's own.