Apartmentner's operator, Dookeobi Sesang, said an outside party used the platform's data-export function twice on October 23 and removed a file containing some users' mobile phone numbers. The company said the file contained only phone numbers, not names, apartment details, resident registration numbers, passwords, or payment and financial information. It detected the incident on November 4, reported it to the Korea Internet and Security Agency and police within 24 hours, blocked the attack IP address, and reset administrator accounts.
Apartmentner warned that the exposed numbers could be used for spam, impersonation messages, or malicious links, while the number of affected users remains undisclosed.