Mate... think a bit more...
SPLINTERLANDS'S RENTAL SYSTEM HAS BEEN HACKED?
I think you might be new to HIVE or you don't know yet things around... Well, then let me help with two things:
First, please moderate your statements because they incur confusions and the wrong perception of what is actually happening. And if you don't care, you will just get downvoted because no one in their right mind accepts the HIVE pool to be withdrawn for this. So, either do more research before posting this, or refuse rewards before posting things like this. This is a recommendation, you do what you wish.
Second, if people got their accounts hacked it was either because of bad passwords/emails... or because they leaked their private keys on a fake website/link. Then the hacker took opportunity to get access to those accounts while people didn't change to new keys. It's the user responsibility, not splinterlands. Remember you own your keys and you own your DEC, even if inside the game.
Depending on this option being set on your account (which I highly recommend):
You can't move DEC (even inside the in-game balance) without active-key... so... unless the active-keys of those accounts were leaked as well, no one can do anything.
If the above option is not set, then you are telling splinterlands that the active key is not required to move assets in-game. I believe the default is to require active-key, so users disabling this need to understand what are they doing.
The system is not broken, people just need to learn more.