What the heck Firefox? Who gave you permission to automatically start on my Windows box? And what bozo VP decided that making auto-start default on install (or be a hidden little opt-out button somewhere) was worth making a little more money in a certain quarter, while you totally damage the Firefox name.
I think some people believe that a computer is always online. Anyhow there is a remedy. [1]
[1] https://www.askvg.com/fix-firefox-automatically-launches-whe...
That article takes 15 pages and 9 ads (some of them very sketchy) to say the following:
Ctrl-Shift-Esc -> Startup -> Firefox -> Disable.
And the facts were pretty slanted. If the page didn’t have so many ads I would say it was probably written by Firefox people.
My sincerest apologies. My old firefox loaded sharply, no ads, just the singular page which seems easy to navigate
I would probably have opted for the first method, from within firefox's settings. Else opted for something different like about:config and searched out DisableLaunchOnLogin setting