Users of one of the most popular browsers, Mozilla Firefox, have recently been able to get acquainted with the new version of the program. If for some of them the update was useful, the owners of PCs running Windows XP and Vista were in for an unpleasant surprise.First of all, among the main innovations is the introduction of WebAssembly support, which competitors can't boast of yet. For the average user, this means improved performance for all sorts of applications and games in the browser. Also important is the lack of support for Silverlight, Java, Acrobat, Unity, Gnome Shell Integration and other plugins using Netscape Plugin API (NPAPI), with the exception of Adobe Flash. True, the latter is still deactivated by default. The browser has received a number of other changes, but the most important of them is the restriction affecting users of older operating systems from Microsoft. The fact is that Firefox 52 will be the last version of the program that can be used by owners of PCs running Windows XP and Vista. Of course, they will continue to receive security updates for some time, but when the period of extended support will be over, users of the outdated browser will be more vulnerable to all kinds of threats from the Internet. Google took similar measures last year when it made it impossible to use Chrome Chrome versions newer than 49 on Windows XP and Vista, as well as outdated versions of macOS. It seems that all users of Windows XP and Vista will have to upgrade to an updated version of the operating system sooner or later. It is not even forced by Microsoft's aggressive policy, but by the refusal to provide the necessary security updates to an increasing number of browsers. Therefore, those who plan to continue to use Firefox should consider installing at least Windows 7, before the period of extended support from Mozilla is over.