How can I gert rid of pop-ups from Mozilla about virus scans?

https://support.mozilla.org/en-US/kb/push-notifications-firefox#w_how-do-i-revoke-the-notifications-permission-for-a-specific-site Are these as small popups on the bottom right corner of Firefox Window?. If so then these are likely web push notifications from site(s) you have allowed to send you notifications. Instead of useful information some may send you junk, spam, fake virus/trojan alerts or fake antivirus scan etc. These are not from Mozilla nor the Firefox web browser. You can revoke the sites from sending you notifications as shown in kb article link above.