iOS 12.1.3 (build 16D39) is an official Apple over-the-air update for the iPhone SE, released on 2019-01-22T18:12:23Z. The update package is 1.28 GB. This is a delta (partial) update that requires 11.4.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: f4f90e619448c4a164efd77a61ec24d47f631b3c.zip.