Scammer or hackers? no one will scam if they're using centralized exchange because it's stupid as the exchanges already hold his identity. If you mean hackers, there's no any centralized exchanges that invulnerable against hacked. Binance as everyone said the most trusted and popular centralized exchange can still got hacked on 2017 if I'm not mistaken.

If Quidax become more bigger, they're just waiting until there's a hacker can find the vulnerability of the exchange.