On June 10, Dota 2's official forums were reportedly compromised, with almost 2 million user email addresses, usernames, passwords and IP addresses available to the hackers.
Related: the best Dota 2 heroes for beginners.
Leaked Source report that passwords on the vBulletin forum "were stored using MD5 hashing and a salt".
The site claims they were able to convert over 80% of the passwords to their plaintext values, thanks to its outdated data protection.
You can use the site to check if your details have been compromised, and there's also a breakdown of the most common domains affected.
Google users seem to be worst off, with over a million hacked, though many of these are apparently disposable email addresses.
There's been no official announcement from Valve as yet.