The Sony Xperia M2 is currently seeing its firmware updated across its different variants. The LTE variants of the Xperia M2 (D2303) and Xperia M2 Aqua (D2403) have been updated to build number 18.3.1.C.1.13.
The Xperia M2 Dual (D2302) has seen build number 18.3.1.B.1.8 roll for those in Saudi Arabia, whilst version 18.3.1.B.0.18 is rolling to a number regions across Europe and Asia.
The D2305 variant of the Xperia M2 has seen build number 18.3.1.A.0.21 roll to Latin America, USA, Thailand, Vietnam, Ukraine and Singapore. In addition, firmware build 18.3.1.A.1.7 was recently certified for this D2305 variant.
Thanks Martin and Vinicius!