iOS 6.1.3 (build 10B329) is an official Apple over-the-air update for the iPhone 4 (GSM / 2012). The update package is 17.52 MB. This is a delta (partial) update that requires 6.1.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 9b3867f63bfb9ba622185956a0e3968d0655a352.zip.