Apple is urging iPhone owners to update their iOS immediately to patch a new security flaw which could give hackers control of their device.
Known as Broadpwn, the bug affects the Wi-Fi chips found in both Android and Apple smartphones and allows an attacker to take over a device remotely while it searches for Wi-Fi.
"An attacker within range may be able to execute arbitrary code on the Wi-Fi chip," Apple wrote on its blog.
The troubling bug only requires users' iOS device to have Wi-Fi turned on for hackers to gain access to assume control of the phone's processor - the central computer runs all the basic system instructions.
Even a passcode will not protect iPhones from the bug, which can bypass the security feature toexploit the weakness.