I was using Terminal on MacOS 11.6 last week and noticed my hostname (machine name?) had changed to Vincentudreault. No idea who/what that is, but when I looked at my machine name in Finder it was still what I expected it to be, as was the "Computer Name" listed in the "Sharing" System Preferences. None of the Sharing services are enabled. I was on a secure (I assume...) Wi-fi network, but it was a shared network at a hostel. I switched to different shells and the incorrect name remained. About 30 minutes after I first noticed it, it had changed back (after opening a new window). My username was always still correct. Attached a screenshot in case it's any help.
Should I assume my machine was compromised and change all my passwords and start panicking?
