This is apparently something that was discovered in Korean MMORPG Tera, in which in a post on Reddit revealed that there was a recently discovered exploit in Tera’s in-game chat that could potentially be used to send malware to other players. This is apparently due to the fact that Tera’s chat interface uses HTML, meaning that it could potentially be used to send coded messages that range from silly images to something more malicious, like malware.
In response to these claims, Tera’s publisher En Masse has since announced that they will be disabling in-game chat and taking it offline while they address the problem. In a post on its forums, the publisher wrote, “There are very serious claims floating around of what this vulnerability potentially allows malicious users to do. We are taking these claims very seriously but, as of this time, we have no evidence that the vulnerability is being exploited in these ways or that any player information has been compromised.”
They also stated that the developers have since been made aware of the issue and are looking into a fix, although when exactly that will happen remains to be seen.