Apple has said it will issue a patch for iOS 7 after hackers demonstrated an exploit for the new mobile operating system.
The flaw would allow hackers to give access to a user's personal data, including photos and emails, without knowing the passcode.
By using the Control Center options screen, accessed by swiping 'up' from the bottom of the device, a hacker can access a user's alarms page. From there a complex combination of button presses lets the user bring up the multitasking screen, and break into any currently running app - bypassing the lock screen security altogether.
The simple hack effectively renders any iOS 7 device - other than the new iPhone 5S and 5C, which do not seem to be affected - open to hackers.
It is unrelated to another 'hack', through which a team in Germany said it is able to spoof a user's fingerprints to get access to their phone.
Apple said it had been made aware of the issue, and would issue a fix.
"Apple takes user security very seriously," an Apple spokesman told the Guardian. "We are aware of this issue, and will deliver a fix in a future software update."