iOS 6.1.3 (build 10B329) is an official Apple over-the-air update for the iPhone 4 (CDMA). The update package is 17.11 MB. This is a delta (partial) update that requires 6.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: c06ff19121155a2264a5f5be1e333c74379989a4.zip.