iOS 12.3 (build 16F5148a) is an official Apple over-the-air update for the iPhone XS, released on 2019-04-29T17:36:05Z. The update package is 156.98 MB. This is a delta (partial) update that requires 12.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 03e0501a2143176083a86e07c78ec84e84ee396d.zip.