iOS 6.1.3 (build 10B329) is an official Apple over-the-air update for the iPhone 4 (GSM). The update package is 883.31 MB. This is a delta (partial) update that requires null already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 61e713aef9569240f29360ad242ff9d15bbace85.zip.