Here are instructions on how to jailbreak your second generation Apple TV using Seas0nPass.
Download the latest version of SeasonPass from here.
Double click to extract the archive you downloaded. Then double click the extract application to launch it.
Click OK to continue pass the tethered jailbreak warning.
You will be asked to sign in as an Administrator. Enter your username and password then click the OK button.
You will be asked to enable UI Scripting. Click the Enable button.
Click the Create IPSW button from the main screen.
Seas0nPass will now download the latest Apple TV firmware file
Seas0nPass will create a custom IPSW file for you.
Once your custom IPSW file has been created, Seas0nPass will ask you to connect the Apple TV to your computer via a micro-USB cable and use the remote to put it into DFU mode by holding MENU and PLAY/PAUSE for 7 seconds. The power cable should be unplugged during this process.
Once your Apple TV has been detected in DFU mode, Seas0nPass will upload some files, automatically launch iTunes, and beginning restoring to the new firmware.