hello damamacd, could you describe where this popup appeared (what you were doing at the time, etc.) & maybe [[How do I create a screenshot of my problem?|do a screenshot]] in case it is happening again. you can always manually check which version you're on and apply any updates available by going to firefox > help > about firefox - the latest version at the moment is firefox 17.0.1. in the past week we have seen some similar reports of malware trying to imitate firefox updates (see [https://support.mozilla.org/en-US/questions/942851] for example). so just to be on the safe site, please do a full scan of your system with the security software already in place and/or a different tool like the [http://www.malwarebytes.org/products/malwarebytes_free free version of malwarebytes].

I received a suspect popup for a Firefox update for the second time today (2013-04-24). Here's a link to a screenshot: [http://i.imgur.com/jM6nLMX.png http://i.imgur.com/jM6nLMX.png] I'm running FF 21.0 beta on OS X 10.7.5.