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 If these are small popups on bottom right corner of Firefox windows then they are likely just web push notifications from sites you have allowed to send you notifications. Instead of useful information they may send you junk, spam or fake virus/trojan alerts etc. You can revoke the sites from sending you notifications as shown in second kb link above.