Redsn0w 0.9.6b4 Update Jailbreaks iOS 4.2.1 Devices

Compatible with iOS devices running Cydia, Redsn0w 0.9.6b4 has been released by the iPhone Dev Team, following their 0.9.6b3 release over the weekend. Devices must be tethered to a Mac or PC for the process to work. [iPhoneDevTeam via RedmondPie]