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

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Starting in Firefox version 57, only extensions built using WebExtensions APIs will work. Not sure if your add-ons are affected? See Firefox add-on technology is modernizing and these Frequently Asked Questions for details.

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?

Once a block is implemented, Firefox will block the unsafe add-on from loading. Blocks can be issued at varying levels depending on the severity of issues found.

  • Soft blocks disable an extension by default, but allow you to override and continue to use the add-on. Soft blocks are issued for non-malicious add-ons.
  • Hard blocks disable an add-on and do not allow you to enable it or override the block. Hard blocks are used when add-ons are found to be malicious.
  • Click-to-activate blocks disable a plugin by default, but allow you to enable the plugin for particular sites. This type of block is issued for non-malicious plugins.

How will I know if an add-on is blocked?

You will see a notification from Firefox with the following message:

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


Add-ons Blocklist Mac1

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

If the add-on has been hard blocked, you will not be able to override the block.

Can I install an add-on after it has been blocked?

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:

The add-on name could not be installed because it has a high risk of causing stability or security problems.

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.

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:

Click to play 1 new

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?

Support ended for all NPAPI plugins except for Flash in Firefox version 52, released March 7, 2017. See this compatibility document and this article for details.

Beginning with Firefox version 52, support has ended for all NPAPI plugins except for Adobe Flash. See this compatibility document and this article for details.

What to do if you see a blocklist notification

If the installed add-on is disabled

Accept the notification and restart Firefox. If you choose to override a soft block, you do so at your own risk.

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.

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.

To make sure you are always using the most up-to-date version of an add-on (extension or theme):
  1. Click the menu button Fx57menu New Fx Menu and choose Add-ons Fx57Addons-icon Add-ons. The Add-ons Manager tab will open.

  2. In the Add-ons Manager tab, select the Extensions panel.
  3. Click on the settings icon Add-on Tools Icon and make sure that the Update Add-ons Automatically menu item is checked.

What unsafe add-ons are on the blocklist?

See the list of blocked add-ons.

// These fine people helped write this article:AliceWyman, Underpass, Tonnes, Michael Verdi, scoobidiver, Andrew, Swarnava Sengupta, Joergen, user669794, Ralph Daub, Lan, Joni, Mark Schmidt, Caitlin Neiman. You can help too - find out how.

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