Hi, Best as can tell it is not a Extension from Mozilla. So no. If can Right Click it and get a URL you can go to the 3 Bar Menu --> Help --> Report Deceptive Site. Or if know the site it popped up on and can Report it to Google : https://safebrowsing.google.com/safebrowsing/report_badware/

I suggest you give your self a Scan to make sure your not calling for them : https://www.malwarebytes.com/

Sid-M said

At times I get "Recommended Security Upgrade" Privacy Enhancer notice. Is this legit? Actually from Mozilla

No it is not legit.

This looks like a fake security update of sorts for Firefox only to perhaps be like one of a many variations of extensions blocked in last while for fake updates. They tend to keep you from accessing your Addons manager (need to start Firefox in -safe-mode) and they do stuff like like remote script injection and search engine redirect. Many examples have been blocked on https://blocked.cdn.mozilla.net/

Firefox updates are done internally Firefox (by way of a .mar file) or by download from mozilla.org like say www.mozilla.org/firefox/all/

Report the url on https://www.mozilla.org/en-US/about/legal/fraud-report/

Can you post the url you got this message from?

I would not be surprised if the fake Firefox update site used the .download or .cool domain as many were from there.