iOS 8.1.2 (build 12B440) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2014-12-09T17:49:04Z. The update package is 64.3 MB. This is a delta (partial) update that requires 8.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: b92bf5bd14494d42369dc7bac8467132472733b3.zip.