The folks over at FireCore LLC announced today that their Seas0nPass had been updated to include an untethered jailbreak for the AppleTV 4.1.1 (iOS 4.2.1). Currently it is only for Mac, but a Windows version "will be available soon."
The FireCore folks credit the Chronic Dev Team for the jailbreak, and they added that the beta 3 version of aTV Flash (black) is compatible with Seas0nPass, GreenPois0n and Pwnage Tool. Full details can be found at the FireCore blog.
Seas0nPass is available for the low, low price of free.