Apple has released iOS 6.1.3 to fix the lockscreen passcode vulnerability that was discovered last month and widely reported by the press. According to the release note, the update also brings improvements to Maps in Japan.
For regular iPhone and iPad users, you can simply go to Settings -> General -> Software Update to upgrade to the latest version of iOS. Alternatively, you can also connect your device to iTunes and apply the update.
Stay away from the Upgrade if you need jailbreak
So if you need Evasi0n jailbreaking and rely on cydia hacks, stay with your current iOS and don’t upgrade to iOS 6.1.3.