You may have ad / mal-ware. Further information can be found in the [[Troubleshoot Firefox issues caused by malware]] article. Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.

It sounds like you are getting random named website claiming a urgent Firefox update. '''This is not from Mozilla or the Firefox web browser'''. The fake firefox-patch.exe and firefox-patch.js files can install things like trojans, viruses, or unwanted software on Windows based on past reports if the user runs them. The updates are done internally in Firefox (with a .mar type of file) whether on Windows, Mac OSX or Linux or by download from mozilla.org like say www.mozilla.org/firefox/all/ You could try using a adblocker extension like uBlock Origin to block theses fake ads. https://addons.mozilla.org/firefox/addon/ublock-origin/ Unfortunately this has gone on for over a month now with one or two new sites reported almost everyday. https://support.mozilla.org/en-US/forums/contributors/712056/ and https://support.mozilla.org/en-US/forums/contributors/712075