Apple have promised to fix an embarrassing flaw in their new operating system, which allows anyone to access important functions when the phone is supposedly locked.
The new iOS 7 software was rolled out as a free update last week, with CEO Tim Cook hailing it as "the biggest change to iOS since the introduction of the iPhone". It faced early problems, with many users complaining about problems downloading it.
Now hackers have discovered that the phone's lockscreen - which should require a password to get past - can be bypassed without one. The glitch affects iPhones 4S and 5, though apparently not the new 5S and 5C.
All that a would-be hacker needs is to press a combination of buttons and make changes using the task manager.
Anyone accessing the phone this way can use texts, emails and photos, as well as Twitter and Facebook accounts.
A spokesman for Apple told The Guardian: "Apple takes user security very seriously.
"We are aware of this issue, and will deliver a fix in a future software update."