Hacking an MMO?

This is a flash game mmo, you don't even need to download anything to play the game. It is called Realm of the Mad God. Realm of that mad got has been hacked twice, once a few months ago, and once about a year ago (both by the same guy) Just go to realmofthemadgod.com to look at the game. First of all this guy gave him self admin privileges and spawned boss enemies in the safezone called the nexus. The next time he hacked it he completely took ever the website realmofthemadgod.com And when you would go there it would take you to a little white text page saying he took the user database and game source code. I was wondering how hard would it even be to hack a into other player accounts like that? It got hacked twice by the same guy it must have some security issues.

It really depends on the game.

This video explains things really well. https://www.youtube.com/watch?v=QX2-h1Kav90

Maybe you can ask this guy: http://www.lostgarden.com/, he was one of the developers of the game.