I am admin of lemmy.world.
Suddenly I was missing the 'admin' icon in the top menu.
I checked, I also wasn't listed on the home page as 'admin'.

I then checked the database, the 'admin' column was 'f' for my account.
There's nothing in the modlog about it, and nothing in the mod_add table.
The 3 other admins are trusted and they are asleep (US timezone).

I have fixed it by updating the person table. But this could be a serious bug or security exploit.