»Random Players appearing in my Island

This bug has been really creeping me out, random players always with a dyed leather armor like in the picture randomly appear in my island, flying and falling real fast, this is the only time I was fast enough to take a screenshot of it, I try to /is warp (TheirName) , but I think these players never existed in this server,

Is this a bug or no? or just some system thingy

 

Hello Sophy,

these NPCs are part of the AntiCheat system. The system randomly checks people for Killaura/Forcefield and if they get hit, the system will know if the user is using Killaura or not. It's not a bug, so yeah it happens to everyone who gets checked from it!