This exploit isn't something you need to worry too much, the only people who have any idea how to do this (and you could probably count them on one hand) aren't going to abuse it or let the information out. Newspaz is right in that this sort of thing has been known about for some time.

The fact remains that jj2 has some major security holes though, and it's something that would be good to fix. The stuff shown in this video isn't even the worst that's possible.