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:

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:

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

1. Click the menu button and choose Add-ons. The Add-ons Manager tab will open.

2. In the Add-ons Manager tab, select the Extensions panel.
3. 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To check if any of your installed plugins are out of date, visit Mozilla's Plugin Check & Updates page.

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.

What unsafe add-ons are on the blocklist?

See the list of blocked add-ons.