As we know Apple TV 4.2.1 update has been released. This update fixes screen flickering issue and other minor issues on Apple TV 2G such as wake from sleep issue, and Audio issue. This update includes performance and stability fixes for Apple TV. Now Firecore has updated Seas0npass to jailbreak iOS 4.2.1 on Apple TV. Using Seas0npass you can jailbreak your Apple TV 2G on Mac OS X and Windows. The instructions to jailbreak Apple TV 4.3.1 (4.2.1) iOS with Seas0nPass is similar to the instructions to jailbreak Apple TV 2G on iOS 4.3 using Seas0nPass.
You should note that it is tethered jailbreak so you have to connect your Apple TV to a computer for a short moment during startup.Click here to download Seas0nPass. After downloading Seas0nPass simply follow the step by step instructions posted here to jailbreak Apple TV 4.3.1 (4.2.1) iOS with Seas0nPass 0.7.2.