Password has been compromised error on my iMac

BE WARY!

Assuming that what was posted is an authentic system alert and not part of an authentic-appearing phishing attempt …

… certainly do NOT follow that included link.

Recognize and avoid social engineering schemes including phishing messages, phony support calls, and other scams - Apple Support

= = =

You can read about how Apple provides it’s own password monitoring function here:

Password Monitoring – Apple Support (AU)

with some additional info here:

Password security recommendations – Apple Support (AU)

+1 @ChooChoo adding:

You can ignore it, over-the-top Apple security alert generated by Apple AI. It’ll do it for passwords it considers too simple. Change at leisure if it bothers you.