Sounds like Malware - ignore that message and run Anti-Malware scans to locate that garbage.

See this - How-do-i-get-rid-of-malware?

. 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}

It would be interesting to know the results of the scans, and whether any damage was done.

Scans vary, some merely display a message or are fake sites. Some do damage only once you interact and follow instructions. Some ransomware lock the browser temporarily, or hate already put malware on the computer by the time you see a message.