iOS 6.1.3 also adds improvements to Apple’s Maps app for users in Japan.
After releasing iOS 6.1 on January 28th, iOS 6.1.1 was released two weeks later to address an issue that impacted cellular performance and reliability for the iPhone 4S.
A mere eight days after that, iOS 6.1.2 was released to address the more widespread and problematic Exchange calendar bug that resulted in increased network activity and reduced battery life.
Hopefully, this is it until we see iOS 6.2.