Mozilla To End All Firefox Support For XP, Vista In June 2018 (bleepingcomputer.com)
An anonymous reader quotes a report from Bleeping Computer: Mozilla announced today plans to stop all support for the Firefox browser on Windows XP and Vista in June 2018. Earlier this year, Mozilla already moved Firefox users on XP and Vista machines to the Firefox 52 ESR (Extended Support Release). The move of XP and Vista users to Firefox ESR was previously announced in December 2016, when Mozilla also said it would provide a final answer on Firefox support for XP and Vista in September 2017. Well, that date has arrived (and passed), and after an internal review, Mozilla announced it would sunset all support for Firefox on the two Windows platforms. Mozilla joins Google, who dropped support for XP and Vista back at version 50, released in April 2016. Microsoft has stopped XP and Vista support in April 2014 and April 2017, respectively.
Firefox is a web browser. What features of Windows does it need that weren't already available in Windows XP?
NX and ASLR are certainly beneficial, security-wise, but that's something the OS takes care of and not something Firefox actively uses. Other than that, displaying web pages has already been possible on XP...
Oh yeah, I guess the API for putting tabs in the title bar has changed. That being said, maybe stop messing with window decorations and keep your stuff in the client area?