This means that any South Korean MapleStory player's information is at risk, including user IDs, names, passwords, and residential registration numbers. This information could potentially be stolen and used for a variety of crimes.
While there's been no word whether actual personal information has been stolen, Nexon nevertheless urged these 13+ million subscribers to change their passwords. The company has contacted the police to ask for a formal investigation.
This comes at an unfortunate time for the company, as Nexon is poised to present its IPO on the Tokyo Stock Exchange in December.