What version of Firefox? Post a screenshot of what you're seeing. I would guess that it's a process that generating messages. You should run these tool from Microsoft to see what process is behind the messages. You would think MS Defender would be helpful.  ;-))

https://learn.microsoft.com/en-us/sysinternals/downloads/process-explorer https://learn.microsoft.com/en-us/sysinternals/downloads/autoruns

I am running Firefox version 142.0.1. The attachment shows only a few of the multiple messages I am getting. I will try the two tools you recommended and give feedback

Hi

Have you tried clearing your browsing history?

The attachment shows only a few of the multiple messages I am getting.

The small popups on bottom right corner of Firefox windows are web push notifications from sites you have allowed to send you notifications from. Instead of useful information some may instead send you junk, spam, fake virus.trojan alerts. Your can revoke these sites as you can see by second link below.

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