According BleepingComputer reports , starting from Firefox 70, if the login information is stored in the browser appears in the leaked database, Firefox will warn - this function by Have I Been Pwned website (data leak check the website) complete cooperation. As early as last September, Mozilla and Have I Been Pwned had to launch an independent service used to check if the account is compromised, called Firefox Monitor .
When the user https://monitor.firefox.com/ when entering their email address on the site, the system will compare the Have I Been Pwned collected leaked database (containing data from China leak of sites and services), if query the data in line, it will show the specific e-mail in which there have been breaches, the user should go change your password immediately.
Currently, Mozilla is this service and integrated password manager Firefox Lockwise and then integrated into Firefox. Upon detection of saved login information was leaked, Mozilla will add an alert icon next to Firefox Lockwise account profile 
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In addition, Mozilla also plans to disclose the statistics to match the case of Firefox Monitor login information involved. As follows:
