Firefox Monitor is a Mozilla service that has partnered with Have I been Pwned to alert users when their email address has been discovered in a data breach. In the past, Firefox Monitor was a standalone service, but starting in Firefox 67 it will now be included as an extension.

As part of a test in November 2018, Mozilla started displaying notifications to Firefox users when they visited a site that historically has had a data breach. You can see an example of one of these breach notifications below.

As spotted by Techdows.com, starting in the current Firefox Nightly build for version 67, Firefox Monitor will now be integrated as a system extension.

Firefox Monitor Extension

While the extension is automatically installed in the Nightly build, it won't be enabled by default. For those who wish to test this new feature, you can go into about:config and add a new setting called extensions.fxmonitor.enabled as shown below.

Adding the extensions.fxmonitor.enabled added setting

Once the setting has been added, you should double-click on it to set it to true.

extensions.fxmonitor.enabled added

Now when you visit a site that has had a data breach, Firefox Monitor will alert you to this using the notification displayed earlier in this article. To test this feature, you can visit one of the known breached sites to see a notification.