The Mintcoin team has today released a mandatory wallet update which removes proof-of-work from the coin entirely, meaning Mintcoin is now 100% proof-of-stake.
The 1.7 wallet update needs to be installed before the block 220,000, and was pushed out as a means to protect against a potential security flaw that was pointed out on the BitcoinTalk forums recently. Due to the low incentive for Mintcoins proof-of-work rewards, it meant the difficulty was so low that it would be easier to perform a 51% attack on the coin.
Removing proof-of-work entirely means that this is now a completely non-issue, and seeing as Mintcoin is already fairly well distributed among users it’s unlikely that security issues will come out of being a pure proof-of-stake coin — although it’s not really something we have experience of at this time.
The Mintcoin developers haven’t really commented too much on the change, aside from this tweet:
Update on potential security issues. As a cautionary measure and since MINT does not really need PoW, we have decided to get rid of the PoW.
Currently the 1.7 wallet has been released for Windows on the Mintcoin website, with Mac and Linux said to be on their way soon.
Update: As several comments have mentioned below, it was in fact the Blackcoin developers that originally discovered this potential security issue and alerted the Mintcoin team.