Although Sony is busy working on the Android 7.1.1 update for its handsets, those who already received version 7.0 continue to get support. The latest such firmware release targets the Xperia XZ and Xperia X Performance, including their dual-SIM variants, and includes Google's January security patch.
The arrival of this update has been reported by more XPERIA Blog users, and it seems there is no change log to talk about at this time. However, it seems that Sony has recently promised to fix an issue that affected some handsets. This issue consists of a reset of the phone's clock after rebooting, so this should be one of the changes. In addition to it, the update also comes with the security patch from Google dated January 1.
After applying the update, the build number of the firmware for the two Xperia handsets mentioned in the beginning should be 39.2.A.0.386.