As with all exchange, it's hard to say if it's truely safe or not. In fact, this is safe until a hacker proves it's not
And sometimes, even if a hacker steal some coins, it can be discovered a long time after the hack. If you want to hold your coin in the long term, you should remove these from an exchange whatever is this exchange. The past has proven that all exchange will be hacked at least once, if it hasn't been already done. That doesn't mean the exchange will have to be shut down, but it's always better to avoid to trust other "useless" parties.
