Add-ons disabled or fail to install on Firefox

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This issue has been fixed with Firefox 66.0.4 and up.

On late Friday, May 3rd, 2019, 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.

Fixes have been released starting with Firefox version 66.0.4. Updates will be rolled out automatically with the latest fixes. If you use Firefox Extended Support Release (ESR), your fix will be automatically delivered when you update to ESR version 60.6.2 or later.

You can also manually update Firefox desktop or you can download and install the most recent Firefox version:

Please see the Firefox 66.0.4 and Firefox 66.0.5 release notes. For Firefox ESR, see the release notes for ESR 60.6.2 and ESR 60.6.3. See also this Mozilla Blog post for more information.

Note: If you're unable to update to the latest Firefox desktop version, we've released extensions to fix issues in older versions of Firefox. See For older versions of Firefox (below).

Known issues and workarounds for things that may not be restored automatically are also listed below.

For older versions of Firefox

The following add-ons are available if you are unable to update to the latest Firefox desktop release. We are working on fixes for other versions of Firefox and will update this article as soon as they become available.

  • Add-on fix for Firefox versions 61-65. If you did not receive the fix for Firefox version 66 or if you are running Firefox version 61 - 65 and do not want to upgrade to Firefox 66.0.5, installing this extension will resolve the issue.

If you are having problems with these add-ons, please file a bug here.

These add-ons have not been widely tested on pre-52 versions of Firefox, but have been reported to work on some machines. If you install these extensions and then upgrade to a supported version of Firefox, please uninstall this extension as it may not be compatible with updated versions.

Known issues and workarounds

Below are known issues and workarounds for things that may not be restored automatically.

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

Under certain circumstances, users updating to Firefox 66.0.4+ may see some of their add-ons disappear (Bug 1549718). The data for those add-ons is not lost, however. Re-installing the affected add-ons should restore the previous state:

  1. Go to
  2. Search for your add-ons and install them individually.

Master password

This is fixed with Firefox 66.0.5. This section applies only if you have 66.0.4. Find what version of Firefox you are using.

If you have a master password that has not been used for a while, the fix in 66.0.4 might not take effect. You can work around this by entering or resetting your master password.

If you know your master password:

  1. Click the menu button Fx57Menu and select Options.Preferences.Settings.
  2. Select the Privacy & Security panel.
  3. Under Logins and Passwords section, click on Saved logins…. This will prompt for your master password.
  4. After you have entered your master password successfully, restart Firefox.

If you don’t know your master password:

  1. Follow the instructions at Reset your Primary Password if you've forgotten it.
  2. Once you have reset the master password, Firefox will restart.
Resetting your master password will remove all of your saved usernames and passwords.

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 (Bug 1549204).

See Multi-Account Containers to set them up again.

Themes will need to be re-enabled

Settings for themes will default back and will need to be re-enabled:

  1. Visit
  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.

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. Click the menu button Fx57Menu and select Options.Preferences.Settings.
  2. Select the Home 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 information.
  1. Click the menu button Fx57Menu and select Options.Preferences.Settings.
  2. Select the Search panel.
  3. Choose a default search engine and additional search engines.
See Change your default search settings in Firefox for more information.

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