Hack that takes control of another player

I don't know if this should be reported as a bug, but a loophole in a program is a bug so I'll put it here:

I played a game in which another person had hacked my controls, and ended up being able to chat as me, play as me, hit buttons such as opening scoreboard and shop, as well as using abilities. (He started chatting as me and used my flash) Link here: Click I suspected it was the Pantheon because he claimed to do so in chat, and he was doing an unnatural amount of damage. In the above link, it shows his largest crit was over 1000 damage, with only a , no Infinity Edge to make crit stronger. Factoring in armor and doing the math, his largest possible crit should have only been around 700-800 AT MAX. I don't know if Riot can pull up the chat logs for this game, but I'm asking for an investigation to be done to patch this loophole.