These sounds like web push notifications from sites you have allowed to send you notifications. They are meant for useful information though some sites have misused them for junk, spam, fake virus alerts also. You can revoke the sites from sending you alerts as you can see in second link. 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