Other clients on the server able to run various commands on me.

[Sykronic]

So today I was playing a on Hell's Gamers. Serious darkrp
and someone who must of been having a very bad day was prop-killing and.. well I called him a name.. or two. he said "That's it i'm going to hack you". First thing that comes to mind is that he's just a HF skid. Then maybe around 10 seconds later he was able to make meatspin open on my screen. Then he added me to gloat. then DDoSed me pretty badly and I just got suspended from my ISP because of it. Unrelated..
but how was he able to open websites on my client?

[Teddi]

It's possible via a few functions in Gmod to send lua to the client and have them open sites etc. Nothing special mind, he never hacked you. just don't play there again.