https://support.mozilla.org/en-US/questions/1258165#answer-1218833 fixed the issue for my v54.

Is it possible to explain this in simple language to a nontechie? Also, I don't have another computer with a newer version of Firefox on it to download whatever that file is that was mentioned. What are the steps to accomplish this on only this computer. You're dealing with an old person here, so as simple as possible explanation. Thanks for your patience.

UPDATE: Mozilla is working on a solution for older versions of Firefox, and this workaround is both unofficial and unsupported. It is possible it might need to be backed out if a different approach eventually is deployed.

Hi NewEnglandAutumn, you are working very hard to stave off time!

Firefox re-verifies extension signatures every 24 hours, so between now and the next time, what you need in your Firefox is a new certificate that won't expire again any time soon.

I will re-post the steps:

Overview

(1) Install the certificate the hotfix would have installed (2) Trigger Firefox to re-verify your extensions (3) Wait until it is back to normal

Steps

(1) Install certificate

Two possible methods: click to download through the certificate installer, or right-click > Save Link As to save a local copy and then import it. There is not an official source for the certificate, so this assumes you trust me!

https://www.jeffersonscher.com/sumo/signingca1addonsmozillaorg_20190504.crt

Screenshot #1 shows the download method. Don't check any of the boxes, just click OK.

To import instead:

Go to the Options/Preferences page, Advanced section, Certificates panel, then click Certificate Manager. Make sure the Authorities tab is selected, then click Import. Find the file you downloaded and open it, then you should get the same dialog as in Screenshot #1, don't check any of the boxes, just click OK. Then you should see the new cert in the list in the Certificate Manager, as shown in Screenshot #2.

(2) Clear the time Firefox last re-verified

This will set Firefox up to check much sooner than it otherwise would check.

(A) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful or accepting the risk.

(B) In the search box above the list, type or paste xpi- and pause while the list is filtered

(C) Right-click the app.update.lastUpdateTime.xpi-signature-verification preference and click Reset on the context menu

Screenshot #3 illustrates the expected result.

(3) Restart Firefox

You can exit Firefox normally, then start it up again. In my tests, it took less than 60 seconds for Firefox to verify my extensions.

Note: You might want to set the true data before restarting Firefox, but perhaps it isn't critical, I have not tested.

Hopefully that will work for you.

There is a system add-on planned for older Firefox versions that do not support the hotfix, so you may want to wait for this add-on.

• Bug 1549604 - ship legacy system add-ons to remediate armagadd-on 2.0