Jailbreakers will take note that iOS 6.1.3, released yesterday, blocks the Evasi0n jailbreak. The Evasi0n jailbreak is the most popular one to date, according to Forbes, which reports that it has been used to jailbreak 18 million iOS devices in the six weeks since its launch.
Ironically enough, even though iOS 6.1.3 blocks the Evasi0n jailbreak, Apple thanked the Evasi0n team in security notes accompanying the upgrade. The people behind Evasi0n say that they probably will not release another jailbreak until the next major release of iOS. What that means for potential jailbreakers is that if you want to jailbreak your iPhone you cannot upgrade past iOS 6.1.2. If you do you'll lose the ability to jailbreak your device until the next major release of iOS.