Sony Mobile has started to seed an update for the single SIM Xperia M4 Aqua with build number 26.1.A.1.128. The PTCRB certified this build for all single SIM Xperia M4 Aqua variants (E2303, E2353, E2306), which compares to previous build number 26.1.A.1.112. So far, this newest update has only been released for the E2303 variant to carriers in Hungary and South Africa and internally (Commercial and Journalists).
The Xperia M4 Aqua Dual (E2312, E2333, E2363) will also shortly receive an update. Build number 26.1.B.1.121 has recently been certified by the PTCRB, which compares to current firmware version number 26.1.B.1.85. We will let you know once it starts to roll.