Sony has started rolling out the Marshmallow update to its Xperia C4 and Xperia C4 Dual smartphones. The update, which brings Android version 6.0, carries a firmware number of 27.3.A.0.122 for the former and 27.3.B.0.122 for the latter. Currently, only the E5303 and E5306 variants of the Xperia C4 and the E5333 and E5343 variants of the Dual model are getting the update. However, it is expected that the remaining variants of the these phones will also get the update soon. It isn't yet clear if the update is rolling out worldwide or limited to select markets. Via
Source: http://www.gsmarena.com/marshmallow_starts_hitting_sony_xperia_c4_and_xperia_c4_dual-news-20486.php
