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 notifications as small popups on bottom right corner of Firefox windows? if so then these may just be web push notifications from sites you have allowed to send you notifications. You can revoke the sites from sending you notifications as shown in second kb article link above.