I set up a fake server to connect to for single player so that I can get the best performance possible. I then used the loop-back address (127.0.0.1) to connect to myself, bypassing all networking. I have two user names: one is the admin and the other is my player. The goal is to not have access to full privileges while playing.
The bug is that my player user accidentally has full privs when logging in after the admin was logged in. I did nothing at all to set privs on either user. I even checked the auth file to find that the appropriate privs were still set in the file (my player user still had just basic/default). This is apparently a bug and is likely related to the IP address of the user.
EDIT: I remembered that I've also experienced this in reverse, with the admin suddenly having basic/default privs.
EDIT 2: The server just now somehow switched the admins between the two users. O.O
EDIT 3: I believe that the bug is related to exiting the server between logins. (I exit by simply closing the window.)
EDIT 4: Switching the player to admin apparently happens when updating the game's settings. The current login name gets input, regardless of whether I was even changing that.