The Sony Xperia X and Xperia XA were released earlier this summer with Android 6.0.1 Marshmallow on board, and although both devices are expected to be upgraded to Android 7.0 Nougat in the future, for now, Xperia X and Xperia XA owners can look forward to a new Marshmallow-based firmware update for all variants. The new firmware build has started to reach customers yesterday and technically speaking it is available for all Sony Xperia XA and Xperia X variants.
The new firmware update for the Sony Xperia XA bumps the build template from the current "33.2.X.2.XX" to build template "33.2.X.3.XX", suggesting that the update might include a few important changes aside from the usual bug fixes. Specifically, firmware build number "33.2.A.3.74" is now being rolled-out on the Sony Xperia XA model numbers "F3111", "F3113" and "F3115", whereas the dual-SIM Sony Xperia XA Dual is being bumped to firmware build "33.2.B.3.74" on model numbers "F3112" and "F3116". Unfortunately, the changelogs are currently missing so we can't go into more detail regarding the exact benefits of applying the latest firmware. Moving on to the Sony Xperia X, the handset is also in queue for a new firmware update, but judging by the fact that the firmware build template hasn't changed, it's likely that the update for the Sony Xperia X is less impactful compared to the software package aimed at the Xperia XA models. The newest update for the Sony Xperia X is identified by build number "34.0.A.2.301", which represents only a minor bump from the previous build number "34.0.A.2.292". As such, the firmware for the Sony Xperia X is likely to contain fewer changes, most likely revolved around usual bug fixing and perhaps quality of life improvements.
As is the case with OTA (over-the-air) software releases, not every Sony Xperia XA or Xperia X unit out there will receive the update at the same time. The process is gradual and the update notification can show up sooner or later from one user to the next. Alternatively, Sony Xperia XA and Xperia X owners can try to trigger the update process manually from the phone's "Settings" menu under "About phone". Just make sure the device has enough battery juice for the entire process.