South Korean crypto exchange Bithumb found that an unauthorized outside party had accessed its internal mobile groupware system and leaked personal information. The breach was identified on October 27 and reported the same day to the Korea Internet & Security Agency (KISA) and the Personal Information Protection Commission.

The attack targeted an outsourced messenger used only by employees. Bithumb says the system is separated from the exchange's trading network and is still checking the exact timing of the attack and whether member data was included in the leak.

Bithumb was one of three South Korean financial firms to report data breaches on October 28.

The incident follows a disclosure by fellow Korean exchange Gopax in early October, which confirmed unauthorized access to some customer accounts since September, with nicknames and login history viewed but no asset losses found.