Tianya.cn, China's best-known online forum, confirmed on Sunday that private information for 40 million users had been leaked, three days after the country's largest programmers' website CSDN reported a similar leak.

On Sunday afternoon, a netizen reportedly told IT media website DoNews that Tianya.cn had been attacked by hackers and 40 million users' passwords had been leaked online. As was the case with CSDN, the leaked usernames and passwords were saved in clear text.

According to Tianya.cn, the forum used clear text passwords in the early days of its existence, changing to encrypted passwords in November 2009. The hacked information affected users who registered before the adoption of the encrypted password system.

Tianya.cn currently has about 60 million registered users in total.

Tianya.cn has launched an emergency response and informed users via email and forum messaging service to change their passwords as soon as possible. The online forum has also reported the case to the police.

China's business press carried the story above on Monday.