It sounds like you are getting a random name website claiming a urgent Firefox update. No it certainly is not legit. The fake firefox-patch.exe can install things like trojans, viruses, or unwanted software based on past reports.

The desktop Firefox is not just for Windows as it is for Mac OSX and Linux also so .exe would not be an effective way to send out Firefox updates. The updates are done internally in Firefox (with a .mar type of file) or by download from mozilla.org like say www.mozilla.org/firefox/all/

Even if Mozilla were to use .exe for Firefox updates on Windows, they would be serving them from a *.mozilla.org url and not from random websites with weird names and a long random stuff on end.

You could try using a adblocker extension like uBlock Origin https://addons.mozilla.org/en-US/firefox/addon/ublock-origin/

Unfortunately this has gone on for a month now with one or two new sites reported almost everyday. https://support.mozilla.org/en-US/forums/contributors/712056/ (fixed link)

thank you for your prompt and informative reply. Hopefully my post and your answer will help others not fall into the Scam..

I've received the same thing for the past few weeks, too; I did see it every day but I've only seen it once in the past few days. I knew it was a virus and never clicked it. I ran antivirus scans and they never found anything, so I'm pretty sure it's coming from infected ads. Just don't click on anything like that which pops up!

I'm getting the same. This has been going on for months. Today, Oct 16th 2016, is the latest occurrence. Always the same happens and appears to be random, regardless of the site I happen to be on. It is a very effective solicitation and I'm sure it has worked many times. Seems to me it would behoove Mozilla to locate the source of this scam and make an effort report or block them. I would even suggest, while it exits, Firefox should not be touting Greater Security. I promise to start documenting the site I'm on when the screen appears.