Are these small popups on the bottom right corner? if so then these may be web push notifications from sites you have allowed to send you notifications from. Unfortunately they can be junk, spam or fake virus alerts from McAfee and such instead of useful information. You can revoke these sites from sending you notifications. 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