Starting in Firefox 70, Mozilla aims to have the browser report when any of your saved logins were found in data breaches. This will be done through their partnership with the Have I Been Pwned data breach site. Mozilla is slowly integrating their independent Firefox Monitor service and the new Firefox Lockwise password manager directly into Firefox. Mozilla also plans on displaying stats for the amount of data breaches your logins have been involved in the browser’s upcoming protection report. It is possible these features will not be ready in time for Firefox 70 but may change as they are being developed.
Source: https://www.bleepingcomputer.com/news/software/firefox-to-warn-when-saved-logins-are-found-in-data-breaches/