iOS 12.3 (build 16F5129d) is an official Apple over-the-air update for the iPhone XS, released on 2019-04-08T17:05:02Z. The update package is 400.61 MB. This is a delta (partial) update that requires 12.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 32b8f2a51ea20380f5baa9fd0c7392defe3b1cdb.zip.