https://support.mozilla.org/en-US/kb/push-notifications-firefox https://support.mozilla.org/en-US/kb/push-notifications-firefox#w_how-do-i-revoke-web-push-permissions-for-a-specific-site Are these small popups on the bottom right corner of Firefox windows? if so then these may be web push notifications from sites you have allowed to send you notifications. Instead of useful information some may send you junk, spam, fake virus/trojan alerts etc. You can revoke these site from sending you notifications as per above second link.