iOS 6.1.3 (build 10B329) is an official Apple over-the-air update for the iPhone 4 (GSM). The update package is 79.27 MB. This is a delta (partial) update that requires 6.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 050f330981e075c4a1f6eaed3d1aaa4f8b8f8cd3.zip.