Interesting. I don't use FF very often. I just went to the "About" window and pressed "check for updates." It responds with "No updates found." I am on 10.0.5.

I notice that the "About" window says "Firefox ESR" and also says "You are currently on the ESR update channel." Any idea what that means?

Some slight Googling leads me to believe that because I downloaded FF from my company, not directly from FF, that my updates are much more limited compared to the "regular" world. That explains why I don't see version 13.x.