but as an ethical thing to be done then he is really worth on getting something because exposing some bugs or something like that.
Based on Bithobo support's clarification earlier, it seems like he didn't inform them about the bug at all. He simply took advantage of it in order to win a lot of games and tried to withdraw his winnings which Bithobo refused.
If this is the actual truth, the ethical thing to do here is to ban him from their site and improve the security of the site drastically in order to prevent more such cases asap.
Let us see how will this pans out. In case, the site should just return the initial deposit of hauzenberg and ban his account afterwards. If they have potential bugs to resolve, they need to provide rewards for those who find bugs on their site so people will not take advantage if they found one. There will always be people like that.