Mozilla has been the last browser developer to offer some kind of support for these old operating systems. Near the end of 2016, they announced that there won’t be any new versions past version 52 (released in March 2017) which will work on them. This version also happens to be an Extended Support Release (or ESR), which means that it won’t receive any major updates, but will receive security updates for far longer than a regular version.
Now, Mozilla has disclosed exactly how much longer version 52 will be supported and that is until June 2018. In the mean time the users are encouraged to upgrade their Windows operating system to the latest version.
Even if Firefox will be secure until next year there’s no telling what holes the OS itself has, because Microsoft has stopped making security patches in 2014 for XP and earlier this year for Vista.