This has happened to me on Linux, Windows, and MacOS. This thread has a screenshot and description of what I mean: This thread has a screenshot and description of exactly what I mean. It's happened to me pretty regularly. This is default FF behavior. https://superuser.com/questions/1451210/how-can-i-make-firef...
On Windows and MacOS this happens to users who launch multiple profiles from the same version at the same time via --no-remote and -P/--profile-manager or in multi user systems where one user updates Firefox and the other person is logged in and running the older version of Firefox.
As Jamie mentioned above Firefox is trying to launch a new process and is unable to find a matching binary. Before Mozilla detected the in-between update state there it was common to see spikes of crashes that were related to process spawning.
The choice Mozilla has is to allow the user randomly crash with a chance of profile corruption or alerting the user about the state and asking the user to trigger an orderly shutdown.
Neither of those use cases apply to me. I haven't even heard of those features before as I don't launch via CLI or use multiple user accounts on my machines.
This would be even rarer but do you use Chocolatey and/or Brew or similar to install Firefox? That could put you back in the Linux package manger situation where a 3rd party application updates the Firefox binary out from underneath it.
