A Pro Hacker

So this guy (STEAM_0:0:5035105) came on to this darkrp server I was on and was able to spawn sweps, give hp, god and noclip even though his ulx rank was still user. So how did he do this(Noob here)? Did find a exploit in ulx or darkrp or garrysmod its self. Also he was making everyone spam Disable sv_allowcslua. And how could an backdoor in a addon do this?

He was probably just an undercover admin, but I don't know much about GMOD exploits.

No his steamid was a new player and was not an admin... I want this hack lol