iOS 12.1.3 (build 16D39) is an official Apple over-the-air update for the iPhone 8 Plus (GSM), released on 2019-01-22T18:09:11Z. The update package is 1.54 GB. This is a delta (partial) update that requires 11.2.6 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 1cdf8d43f2cdf3431b6991b289c03829e485eefd.zip.