MtGox

In June 2011 the MtGox bitcoin exchange suffered a significant security breach where attackers gained access to the user database. The incident involved the compromise of an administrative account which allowed hackers to manipulate exchange rates and access sensitive user information. The leak exposed personal data of approximately 61000 registered users. Compromised credentials included usernames and email addresses along with passwords stored as MD5CRYPT hashes. This event was one of the first major security crises in the cryptocurrency industry and highlighted severe vulnerabilities in exchange security protocols at the time.