Even though this might only be a TETHERED jailbreak, it will be great news for some. Firecore has recently updated their jailbreak tool Seas0nPass to add support for Apple TV running the latest software 5.2.1, which was released on March 19, 2013 alongside iOS 6.1.3.
The Seas0nPass software is compatible with the 2nd-generation Apple TV, unfortunately the 3rd-generation TV is still not supported. Jailbreaking your Apple TV opens a wide range of options that Apple restricts and allowing a user to run third-party applications.
Seas0nPass is available for free for both Windows and Mac. Head on over to the firecore website to get more info and details on how to jailbreak your 2nd