It was just a matter of a couple of days before the first iPhone 4 was shipped that the famous guy who ported Android to iPhone was able to exploit an old leak in the new iOS 4 to jailbreak his iPhone 4.
Download iOS 4 for iPhone 3G, 3Gs and 4 and iPod Touch 2G and 3G
The actual code that was used to get root access (SSH) to the iPhone 4 (for those who don’t know, getting root access effectively enables anyone to jailbreak) is of “Spirit” jailbreak tool that was developed by Comex but since he does not has an iPhone 4 yet, PlanetBeing used his code to jailbreak his new iPhone 4. Here’s his tweet:
Then iPhoneDevTeam followed with the famous iPhone hacker, MuscleNerd posting an image of his iPhone 4 running Cydia which again means that he has also successfully JB (Jailbroken) his iPhone 4 too. It’s not sure whether he used Spirit’s JB code or his own. Here’s his high-res screenshot of Cydia running on iPhone 4:
And here’s the tweet of @musclenerd of the iPhoneDevTeam about his successful jailbreak:
The infamous George Hotz famously known as @geohot has not updated his jailbreak tool for iPhone 4 yet. Stay tuned for any updates on that.
Update 1
Just to make it more obvious and remove any doubts that you might have, @musclenerd has just posted a screenshot showing full root access to his jailbroken iPhone 4 using Spirit JB:
Note: It’s been noted that this jailbreak is only for testing purposes for now but a release of Spirit jailbreak tool for iPhone 4 is eminent anytime now.