https://addons.mozilla.org/en-US/firefox/extensions/

https://addons.mozilla.org/en-US/firefox/addon/ublock-origin/ https://addons.mozilla.org/en-US/firefox/addon/ghostery/ https://addons.mozilla.org/en-US/firefox/addon/adblock-for-firefox/

Please let us know if this solved your issue or if need further assistance.

You can request new or changed features via the Feedback page: https://qsurvey.mozilla.com/s3/FirefoxInput/

Seriously, there are many ad blocker extensions available for Firefox, so I doubt if Mozilla will ever offer a built in ad blocker. And being a user of Firefox from almost day one (Aug 2002, before this browser was even named Firefox) a built-in feature would definitely come up short of many features that existing ad block extensions offer.