Hi, it's a scam to infect you with malware! NEVER EVER click on anything like that.

If you are in any doubt about the authenticity of update pop-ups etc., it's 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 release.

If your question is resolved by this or another answer, please take a minute to let us know. Thank you.

. Whenever you get a message / popup like that;

DO NOT USE ANY OF THE PROVIDED LINKS OR ANY PHONE NUMBERS ! !

Such messages are only Spam that could lead you to Fake Support. Not only can they damage or hack your system, they charge you to do so.

You can 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}