Damn, I think this is not a hack but an exit scam, the site does not have a good reputation anymore, I hope I'm wrong but I believe getting into exit scam is more probably than being hack.
It doesn't matter whether it's hack or exit scam, since their uses will suffer losses either way. If they're hacked, i doubt they could recover or even bother reimburse user loss since they have bad reputation.
Of course, the main rule has always been to never leave big funds at exchanges, isn't it?
Might be difficult for lesser altcoin which don't have good light wallet. Usually you're either forced to use crap or full node wallet.