hi ksergey2712, sorry for this mishap! mozilla is considering in which way the problem should be addressed for users on legacy versions at the moment.

this would be a workaround i can offer in a personal capacity in the meantime (basically the same steps that the automated hotfix was performing in the still supported versions of the browser):

=

(1) Download the fixed certificate

The updated necessary certificate is available for download at https://hg.mozilla.org/releases/mozilla-release/raw-file/tip/security/apps/addons-public-intermediate.crt

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 a dialog - 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 #1.

(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 #2 illustrates the expected result.

(3) Restart Firefox

You can exit Firefox normally, then start it up again. It should take a few seconds, but then your addons should turn back into an active state

Hopefully that will work for you.

philipp said

...this would be a workaround i can offer in a personal capacity in the meantime (basically the same steps that the automated hotfix was performing in the still supported versions of the browser)...

Hi phillip:

Thanks for posting instructions for manually installing the updated certificate in FF ESR v52.9.0. I tried it today and that seems to have fixed the problem on my Vista SP2 machine. Just a reminder to other Win XP/Vista users that If you previously implemented the temporary workaround and changed xpinstall.signatures.required to FALSE in about:config, remember to change this setting back to TRUE after importing the updated certificate.

Do you have any idea if Mozilla is eventually planning to post a revised v52.9.0 installer at https://www.mozilla.org/en-US/firefox/new/ that includes the updated certificate? FF ESR doesn't have a Shield Studies feature and my Help | About Firefox | Check for Updates currently reports "You can not perform further updates on this system" so I'm not even sure that releasing an ESR v52.9.1 update would be a viable option.

32-bit Vista Home Premium SP2 * Firefox ESR v52.9.0

There is a legacy system add-on planned for older Firefox versions that do not support the hotfix.

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

(please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html)

Hi ksergey2712:

Just an update to let you know that an official bug fix has now been released for Firefox ESR v52.9.0.

The Mozilla blog Add-ons Disabled or Failing to Install in Firefox was updated today (12:51 EST May 13, 2019) and now notes that an extension has been posted on the official Mozilla AMO store at https://addons.mozilla.org/en-US/firefox/addon/disabled-add-on-fix-52-56/ that should automatically "re-enable extensions that were disabled on May 3, 2019 for Firefox versions 52 - 56".

I already followed philipp's 07-May-2019 instructions <above> and manually installed the updated certificate in my FF ESR v52.9.0 browser so I don't plan to install the new extension posted today on the Mozilla AMO store unless I hear there's a good reason to do so (e.g., that the certificate delivered by the extension posted on the AMO is actually newer than the one I already imported on 07-May-2109).

32-bit Vista Home Premium SP2 * Firefox ESR v52.9.0