Update on Firefox Support for Windows XP and Vista
Dec 23, 2016 - "In approximately March, 2017, Windows XP and Vista users will automatically be moved to the Firefox Extended Support Release (ESR*).
Firefox is one of the few browsers that continues to support Windows XP and Vista, and we expect to continue to provide security updates for users until September 2017. Users do not need to take additional action to receive those updates. In mid-2017, user numbers on Windows XP and Vista will be reassessed and a final support end date will be announced. In the meantime, we strongly encourage our users to upgrade to a version of Windows that is supported by Microsoft. Unsupported operating systems receive no security updates, have known exploits, and are dangerous for you to use. For planning purposes, enterprises using Firefox should consider September 2017 as the support end date for Windows XP and Vista. For more information please visit the Firefox support page**."
"... Firefox version 52 will be the last complete update for Windows XP and Windows Vista. Security updates will be released, but no new features... Firefox is one of the only browsers to offer any support for Windows XP and Vista. Microsoft itself ended support for Windows XP in 2014 and will end support for Windows Vista in 2017. Unsupported operating systems receive no security updates, have known exploits, and can be dangerous to use, which makes it difficult to maintain Firefox on those versions.
Firefox security updates for XP and Vista users will continue until September 2017, although new features will not be offered. In mid-2017, a final support end date will be announced based on the number of users still on Windows XP and Vista..."