Minecraft Exploit. Player/Hacker creates Entities with NBT tags using GM1

The exploits of that guy had been already reported before, but now he found a new way to create commands blocks with certain command pre made and without having any op-rights, by just using gm1.

https://www.youtube.com/watch?v=HvIkGbSBltU

He also created "crash items", that are able to corrupt other players inventories. Crashing thier client and not letting them rejoin a server.

https://www.youtube.com/watch?v=-enNcq0xzXg

I know that these exploits are made by his hacked client. But they work on every server, modded or vanilla. And this is a server sided security issue.