Apples latest update to iOS, released Friday (Feb. 21), doesnt seem important at first. But the update actually fixes a serious security flaw, possibly caused by a single stray line of code, which leaves hundreds of millions of iPhones and iPads vulnerable to hackers. If you have a device running iOS 6 or 7, and youre not connected to a strangers Wi-Fi network, patch it now — weve got instructions below.