Delightful: unauthorized access to the Meruhaikun email delivery system

Servers of the Meruhaikun email delivery system run by Delightful were accessed from 11 to 17 June. Delightful detected unusual access on 15 June and cut off all servers by 17 June. According to findings passed to customers, the attacker exploited a system vulnerability to gain administrator rights, used the credentials obtained to spread to several servers, and extracted recipient data from the database. Its report of 14 August confirmed that recipient data (email addresses and more) of some customers leaked, and the final report received by the Japan Society of Engineering Geology puts the total at 1,679,242 people. Many companies and groups that used it for newsletters disclosed their impact.