GTA Online has quite a few glitches, some are funny as demonstrated in YouTube videos, some are exploited and spoils the game for others, one of the glitches that is particularly bad is when someone can hide in plain sight.
I’ll show what I mean in a video I recorded, but to put it in text, it means someone can walk through something like a wall or drop in to a building and be able to shoot other people without being seen. Sometimes, you can see the person through a window of a building, they can’t be touched due to being inside, but can still attack you.
It’s an unfair advantage for the morons who exploit the glitch to grief other players, but could be useful for legit players who want to level up without being a dick.