Mozilla is adding an ad blocker to Firefox Focus 9.0, which is scheduled to be released next month. Firefox Focus is Mozilla’s stripped-down light-weight mobile browser for Android and iOS that is designed to enhance a user’s privacy by not saving passwords, blocking ad and content trackers, and offering a lean experience without any bells and whistles. Mozilla will be running an A/B experiment where 50% of users will have all ad blocking features enabled, while the other 50% will have the ad blocker disabled and its settings hidden from the interface.
Source: https://www.bleepingcomputer.com/news/software/mozilla-is-adding-an-ad-blocker-to-firefox-focus-90/