iOS 7.1.2 (build 11D257) is an official Apple over-the-air update for the iPhone 4 (GSM), released on 2014-06-30T18:00:03Z. The update package is 152.46 MB. This is a delta (partial) update that requires 7.0.4 already installed. This update is currently signed by Apple, so it can be applied from Settings › General › Software Update.

Payload file: 1600dc06be303bcb94624571a3a10a3e0f1fff9a.zip.