Blocklisting (or blocking) is an action of last resort taken to protect Firefox users against add-ons (extensions, themes and plugins) that violate Mozilla's add-on guidelines.

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

Once an add-on has been blocklisted, it will not appear in the gallery of addons.mozilla.org until the developer uploads a new version that addresses all issues that resulted in the block request.

Additionally, Firefox will prevent you from installing an unsafe add-on that is on the blocklist by displaying this 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?

What to do if you see a blocklist notification

If the installed add-on is disabled

Accept the notification and restart Firefox.

Extensions and themes

1. Click the menu button , click Add-ons and themes and select Extensions.
2. On the "Tools for all add-ons" menu, make sure that the Update Add-ons Automatically menu item is checked.

Plugins

Check to see if there's an updated version of your plugin. If there are no plugin updates available, you may need to contact the developer of the plugin that was blocked.

Installation

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. Please be aware that some blocks may be permanent and you may need to find an alternative add-on.

Can blocks be lifted?

Depending on the severity of the violation, the history of the developer, and other relevant factors, some blocks may be lifted once the developer uploads a new approved version. If that happens, users who had previously downloaded the add-on will immediately be able to use it again once its listing goes live again on addons.mozilla.org.

What unsafe add-ons are on the blocklist?

See the list of blocked add-ons.