Apple released a minor software update for iOS devices. iOS version 6.1.3 fixes a bug that could allow someone to bypass the passcode to access the phone. It also adds improvements to Map in Japan. iOS 6.1.3 applies to the iPhone 3GS, iPhone 4, iPhone 4S, iPhone 5, the iPad 2 and later, and the fourth-generation and iPod touches.
Apple users are recommended to update their devices over the air by opening the Settings screen, tapping on General, choosing Software Update, and then downloading and installing the latest version directly.
GSMArc.com : List of ios devices