The LTE variants of the Sony Xperia M2 (D2303 and D2306) and the Xperia M2 Aqua (D2403 and D2406) have been bumped to the latest firmware with build number 18.3.1.C.1.17, which introduces a new bootloader and a separate recovery partition.

Xperia M2 LTE and M2 Aqua
Xperia Blog

The new firmware reportedly includes similar features found on the previous build 18.3.1.C.1.16 that started to roll out recently.

There are no further details available at the moment concerning the new firmware's changelog or the exact features ported into the latest build.

Nevertheless, it is ascertained that the firmware (18.3.1.C.17) is currently being pushed to a few select regions only. Those who cannot wait for the official release of the firmware in their country or region can download the latest FTF firmware from the direct download links provided below.

DOWNLOAD FTF firmware files

Xperia M2 (D2303) 18.3.1.C.1.17 – Middle East Generic [Android 4.4.4]
Xperia M2 (D2306) 18.3.1.C.1.17 – US Generic [Android 4.4.4]
Xperia M2 Aqua (D2403) 18.3.1.C.1.17 – Switzerland Generic [Android 4.4.4]
Xperia M2 Aqua (D2406) 18.3.1.C.1.17 – Commercial and Journalists [Android 4.4.4]

[Source: XperiaBlog]