Over the weekend, hackers breached the official forum of the Unity cross-platform game engine developed by Unity Technologies. The attackers claim to have stolen user data, but the company has denied that any sensitive information has been compromised.

The hacker group calling itself OurMine has defaced the Unity forum and abused it to send out emails to registered users via a built-in mass email feature. In their message, the hackers informed recipients that they had gained access to a database containing the details of 2 million users, and advised everyone to change their passwords.

In a blog post published on Monday, Unity confirmed the breach and blamed it on “poorly implemented password routines.” However, the company claims the hackers only accessed “a limited set of data,” and assured users that no passwords, payment information or other Unity services had been compromised.

“No passwords were lost in the breach, but we still recommend a password change due to possibility of the group having emails and passwords from another source, which could be used to access their account,” Unity representatives said.

The company says it does not store passwords in clear text, and it plans on rolling out additional account protections in the next few weeks, including two-factor authentication, alerts for logins from unrecognized devices, and new password policies.

The forum was taken offline following the hack, but it has now been restored. Some posts may have been lost as the forum was restored using a backup timestamped April 30, 14:01 CEST.

Gaming-related forums have often been targeted by cybercriminals. The list of breached websites includes ones dedicated to Bohemia Interactive’s DayZ, Epic Games’ Unreal Engine and Unreal Tournament, and Valve’s Dota 2.

OurMine, which describes itself as a group that provides security services, has targeted numerous high profile social media accounts in the past months.

The hackers have taken over the online accounts of Sony Music Entertainment, Facebook CEO Mark Zuckerberg, Google CEO Sundar Pichai, Spotify founder Daniel Ek, and many others. The group recently also hijacked several high profile YouTube accounts.

Related: Flaw in Unity Web Player Allows Theft of Personal Data

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