Hi, yes you are right, it's a fake update designed to infect you with malware which we have seen a lot of recently! NEVER EVER click on anything like that! Please see the article - [[I found a fake Firefox update]]. If you are in any doubt about the authenticity of update pop-ups etc., it's always best to ignore them and check for yourself by opening the 3-bar menu > Help (question mark at bottom right) > About Firefox. Alternatively, you can press the Alt key to bring up the main menu bar > Help > About Firefox. More - [[Update Firefox to the latest version]]. A possible workaround that seems to work for some, is to install an ad-blocker, such as - https://addons.mozilla.org/en-US/firefox/addon/ublock-origin Or, but this may be less effective - https://addons.mozilla.org/en-US/firefox/addon/adblock-plus ''If your question is resolved by this or another answer, please take a minute to let us know. Thank you.''

Not all Firefox user on Windows get this however once they do you have a greater chance of getting it again. Ad blocking extensions as mentioned have been a good way of stopping these malicious ads.