Download Firefox 12-51 52 Esr =link= Here

: Versions 51 and 52 ESR were released just before the "Quantum" update (Firefox 57), which transitioned exclusively to WebExtensions and dropped support for "Legacy" add-ons. Where to Download

Mozilla previously maintained an FTP server ( ftp.mozilla.org ) with all older releases, but this was shut down in 2023. You can still access an unofficial mirror or use the Internet Archive's Wayback Machine . Download Firefox 12-51 52 Esr