I assigned a player their own area and set the permissions to "Owner". However someone named jeim 76561198336041209 came in and destroyed his buildings and terrain. In the logs it said he used explosives. Server is set to "survival" and creative mode should not work.
The player Saturno72 or Michael, as he called himself when he came to my server, placed blueprints in a player's base. I banned him offline. In my opinion, the permission system is also way too complicated and needs to be simplified.