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

https://support.mozilla.org/en-US/kb/push-notifications-firefox#w_how-do-i-revoke-web-push-permissions-for-a-specific-site https://support.mozilla.org/en-US/kb/push-notifications-firefox

It could be - but they came without any sort of provocation - they just started going crazy. Now wierd website was visited and I literally did nothing. I assumed that Firefox would not let such things happen so I assumed that they were legitimate.

There were three different versions and a couple had a url that looked totally external. I was not on any unusual site nor did I invite any notifications - they are turned off for almost everything. These only arise in the Firefox browser - I tried the other two and there were no problems. I am assuming therefore that something penetrated the browser