Mozilla announced that in June 2018, it plans on finally dropping its Firefox browser on Windows XP and Windows Vista completely, encouraging those who use Firefox through those platforms to upgrade Windows as soon as possible.
Mozilla stopped its support of Windows XP and Windows Vista when it released Firefox 53 in April 2017. However, users of these platforms were moved to Firefox Extended Support Release, designed for larger groups who maintain a desktop environment, allowing them to still receive security updates until a decision on when their support would end was made.
Because Microsoft dropped all its support for Windows XP in 2014 and for Vista in April of this year, users of XP and Vista cannot upgrade to newer versions of Microsoft's browser. Therefore, XP and Vista users resorted to third-party browsers, like Firefox, which is probably why Mozilla has continued its support this long. But with XP and Vista having only 6.12% of the market share combined as reported by Net Applications, Mozilla has finally decided it's time for it to end.
With the end date drawing near, Mozilla prompts users to upgrade to a Microsoft supported version of Windows as soon as possible, stating, "unsupported operating systems receive no security updates, have known exploits, and are dangerous for you to use."
