Sooo, uhh
We've discovered that playing ANY Unity WebGL Game in the Firefox Browser is bugged. When either of us enter Fullscreen Mode and click the left mouse button, it selects  the whole game window as if it was selecting a text object.
Can anyone else replicate this bug?

Link to some random WebGL Game to test it: https://crowfox-creatives.itch.io/ryans-drive

I noticed that while testing, but I forgot about it because I switched the default template to this:

https://seansleblanc.itch.io/better-minimal-webgl-template

I haven't had the problem and it seems to work for my game:

https://awesomeonpurpose.itch.io/absurd-aracana

Related to this?

https://discussions.unity.com/t/odd-issue-with-focus-in-firefox/1651226