I looked at www.pathoes.com. It is a legitimate web site and not dangerous. However, the /galleries/ postfix results in an "error 404 not found" page. If your pop-up purported to be about a Firefox update, it would be safest to not cllick on it. You might make sure that your version of Firefox is current, but don't do it via the patheos route.

. Whenever you get a message / popup that software / files need to be updated;

DO NOT USE ANY OF THE PROVIDED LINKS

While this may be a legitimate message, it could also be Malware or a Virus. Any time you want or need to check for upgrades, go to the web site of the True Owner of the program in question. For example, to check out Firefox, go to Mozilla.org. {web link}

You can also report such a site at; Google Report Phishing Page {web link} which is the same when done while on site by going to Help > Report Web Forgery

Help us safeguard Mozilla’s trademarks by reporting misuse {web link}