Sony Xperia Z2 users are reporting that they are receiving a firmware update to build number 23.4.A.1.200. The update appears to only be live for those with the D6503 variant with a Nordic NCB handset (CDA: 1282-0508). This is the same build number that was certified for all of the Xperia Z2 and Z3 series recently.
Strangely, despite this being a newer build, it is fully exposed to the Stagefright exploit. The update doesn’t appear to be widely distributed, so you should wait until it hits PC Companion (although you may want to wait if the Stagefright exploit hasn’t been fixed).
Sony Xperia Z2 FTF firmware files – Android 5.1.1 Lollipop (23.4.A.1.200)
Sony Xperia Z2 Tablet FTF firmware files – Android 5.1.1 Lollipop (23.4.A.1.200)
Pictures via XDA.