Add-ons that cause stability or security issues are put on a blocklist

Revision Information
  • Revision id: 601
  • Created:
  • Creator: AliceWyman
  • Comment: Windows Presentation Foundation plugin is no longer blocklisted
  • Reviewed: No
  • Ready for localization: Yes
  • Readied for localization by: AnonymousUser
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Add-ons (extensions, themes, and plugins) that are known to cause stability or security issues with Firefox are put on a "blocklist."


What does the blocklist do?

Disables unsafe add-ons

Firefox will block the add-on from loading and present you with the message:

Firefox has determined that the following add-ons are known to cause stability or security problems
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To prevent these add-ons from running, click Restart Firefox.

Blocks unsafe add-ons from being installed

When you try to install an add-on that is on the blocklist, Firefox will block the installation and display the message:

The add-on name has a high risk of causing stability or security problems and can't be installed.


Steps to take

If the installed add-on is disabled

Check to see whether there is an updated version of that add-on:

  • (Extensions): Click on the Tools menu, select Add-ons, select the Extensions panel, and then click Find Updates. If Firefox finds an update, you will be prompted to install it and restart Firefox.
  • (Themes): Click on the Tools menu, select Add-ons, select the Themes panel, and then click Find Updates. If Firefox finds an update, you will be prompted to install it and restart Firefox.
  • (Plugins): To check if any of your installed plugins are out of date, visit Mozilla's Plugin Check & Updates page.

If there are no updates available, you may need to contact the developer of the add-on that was disabled.


Installation blocked

If you were blocked from installing an add-on, check to see if there is an updated version of the add-on you were trying to install.

If there is not an updated version to install, you may need to contact the developer of the add-on that was blocked.


What add-ons are on the blocklist?

See list of blocklisted add-ons.