iOS 9.9.12.1 (build 16B5059d) is an official Apple over-the-air update for the iPhone XS, released on 2018-09-18T17:20:19Z. The update package is 2.65 GB. This is a full OTA update that can be applied from any compatible base version. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: ef40c57e72ba1fb81200c7030dfe4f499e2f7bfb.zip.