Sony has rolled out a new firmware update for their Xperia Z2, Xperia Z3 and Xperia Z3 Compact with the build number 23.4.A.0.580. This new firmware brings the fix for the Stagefright exploit which was reported recently. Still the update has rolled out only for European carriers of Xperia Z2 (D6503), Xperia Z3 (D6603), Xperia Z3 Compact (D5803).
So far the update is live for carriers. This looks like a carrier specific update. but we will see what happens later. If you have installed it. Just let us know about more changes.