Add-ons (extensions, themes, and plugins) that violate Mozilla's add-on guidelines are put on a "blocklist".

What does the blocklist do?

Disables unsafe add-ons

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

Firefox has determined that the following add-ons are known to cause stability or security problems

To prevent these add-ons from running, click Restart Firefox.

Blocks unsafe add-ons from being installed

When you try to install an unsafe 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.

Prevents plugins from running automatically

Firefox can prevent a plugin from running automatically (which prevents many issues). When Firefox blocks a plugin you'll see a message similar to this:

You can then choose to run the plugin or update it (if an update is available). To learn more, see Why do I have to click to activate plugins?

Steps to take

If the installed add-on is disabled

Extension or theme

At the top of the Firefox window, click on the Firefox buttonOn the menu bar, click on the Tools menuAt the top of the Firefox window, click on the Tools menu, and then click Add-ons. The Add-ons Manager tab will open. Click the menu button and choose Add-ons. The Add-ons Manager tab will open.
In the Add-ons Manager tab, select the Extensions panel.
On the "Tools for all add-ons" menu, make sure that the Update Add-ons Automatically menu item is checked.

Plugin

To check if any of your installed plugins are out of date, visit Mozilla's Plugin Check & Updates page.

Note: If there are no updates available, you may need to contact the developer of the plugin that was blocked.

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.

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

What unsafe add-ons are on the blocklist?

See the list of blocked add-ons.

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

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

Table of Contents