A small firmware update with build number 14.3.A.0.761 has been certified for the Xperia Z1, Xperia Z Ultra and Xperia Z1 Compact. The Android 4.4.2 KitKat firmware is likely to offer bug fixes over the previously released firmware with build number 14.3.A.0.757. The last firmware fixed the sound bug issue prevalent in the first release of KitKat and quashed a number of bugs that people were having. We expect this new release to bring further stability.
Xperia Z1 firmware build 14.3.A.0.761 certified for C6902, C6903 and C6906 models
Xperia Z Ultra firmware build 14.3.A.0.761 certified for C6802 and C6833 models
Xperia Z1 Compact (D5503) firmware build 14.3.A.0.761 certified