On late Friday, May 3rd, we became aware of an issue with Firefox that prevented existing and new add-ons from running or being installed. We are very sorry for the inconvenience caused to people who use Firefox. We are working hard to fix the add-ons issues. We will keep this article updated with our progress.

Known issues and workarounds

Add-ons appearing as unsupported or disappeared from your about:addons page.

Their data is not lost because it is stored locally on your profile directory. (Bug 1549129). Re-installing the add-ons will recover the data:

1. Go to https://addons.mozilla.org/firefox/.
2. Search for your add-ons and install them individually.

Container add-ons

Containers add-ons may reset to their default state. If add-ons that use the Containers functionality, like Multi-Account Containers and Facebook Container, were disabled as part of this problem, any lost site data for containers, as well as deleted custom containers you may have configured, will not be recovered by this new release.

Data that may be lost for Container add-ons include configuration data for which containers to enable or disable and container names and icons. Locally-stored data for the container (cookies and permissions) are also affected. See Bug 1549204.

See Multi-Account Containers to set them up again.

Themes will need to be re-enabled

Themes will default back and will need to be re-enabled:

1. Visit https://addons.mozilla.org/firefox/themes/.
2. Click on the theme you want to install.
3. Click the Install theme button. Click Remove if you change your mind. Your changes will apply automatically.

See Use themes to change the look of Firefox or Built-in themes in Firefox - alternative to complete themes to learn more about themes.

Home page and search<h2> If your home page or search settings are set by an add-on, they will be reset to their default settings (Bug 1549192) To change them back:

Home page

1. Type 'about:preferences in your address bar.
2. Click Home on the left panel.
3. Choose your desired settings for the Home page and new windows and New tabs by clicking the drop-down menu next to each one.

See How to set the home page for more.

Search

1. Type 'about:preferences in your address bar.
2. Click Search on the left panel.
3. Choose a default search engine and additional search engines.

See Manage Firefox search settings for more information.

Our team has identified and rolled-out a fix for all Firefox Desktop users on Release, Beta and Nightly. The fix will be automatically applied in the background within the next few hours. No active steps need to be taken to make add-ons work again.

To deliver a fix on short notice, we are using the Studies system. This system is enabled by default, and no action is needed unless Studies have been disabled. Firefox users can check if they have Studies enabled by going to:

1. In the Menu bar at the top of the screen, click Firefox and select Settings (select Preferences on older macOS versions).Click the menu button and select Settings.
2. Click Privacy & Security on the left panel.
3. Put a check mark next to Allow Firefox to install and run studies (scroll down to find this setting).

   

It may take up to six hours for the study to be applied to Firefox. To check if the fix has been applied, you can enter about:studies in the address bar. If the fix is active, you’ll see hotfix-reset-xpi-verification-timestamp-1548973 as shown:

You may also see hotfix-update-xpi-signing-intermediate-bug-1548973 listed, which is part of the fix and may be in the Active or Completed section.

We are working on a general fix that doesn’t use the Studies system and will keep this blog post updated accordingly.

We will share a more substantial update in the coming days.