So in summary. Mintcoin has an attack demonstrated against it which proves it is vulnerable.
Blackcoin has suffered no attacks because it is PoS only and no known attacks have been made against the protocol. Yes an exchange was hacked but lots of exchanges get hacked especially bitcoin ones.
wasn't there a hard fork that coincided with people losing a lot of blackcoins or was that just around the same time? I really am curious about what happened as I know the exchange was blamed
The exchange used a stupid feature which has been around in the clients since bitcoin. That messed up their user's balances within their blackcoin client. That's how users withdrew more than they had and could have negative balance. The total wallet, however, did not have negative balance.
Ohh I see I just remember a bunch of issues with blackcoin wallet balances and figured it was all connected