Techcrunch, a gadget blog, called the exploit "a massive backdoor to some of the iPhone's core functions".
Posted on YouTube by a blogger identifying themselves only as VideosdeBarraquito, the Apple hack has been viewed by nearly 4,000 people, and replicates a similar flaw with earlier software, iOS 4.1.
According to the paper, the process can be triggered by aborting an emergency call and then executing a dozen simple button presses to fool the device into keeping the iPhone open.
The flaw means that the iPhone opens the phone app, giving access to the main systems including call logs and messages, the paper said.
It relies on precise timing, but can easily be replicated by any user, it added.