Java Exploiting mods like gmod lua kids exploit addons?

Basicly the title says it all, there are probably very popular horribly made mods out there, do any of them provide any malicious use to exploit? People do it all the time on gmod since lua is so easy but you don't hear too much about java exploiting in minecraft, more just basic hacks.

been, ages maybe new minds, does any1 here mess with packets?

Bumped own thread because it is definitely possible, MFR has an exploit that lets you spawn rockets anywhere with any velocity.