Have not received any security updates since installation. Why?
The directions to set up or check for updates starts with going to system and then administration...update manager. Can't find system. I have not had a single update since I had this done (ubuntu, linux, firefox)
Opaite Mbohovái (2)
Your Firefox is fully updated (44.0.2, which is the latest release). As for your other programs on your computer, we aren't able to help with why they aren't updating.
You appear to be using the Ubuntu supplied version of Firefox so Firefox updates comes from them and not Mozilla.
Firefox 44.0.2 is the current as said and the next Release Firefox 45.0 will be out from Mozilla.org on March 8.