Firmware build 32.0.A.6.152 for Xperia Z5
Xperia Z5 is no more vulnerable to Stagefright bug with the new firmware build 32.0.A.6.152 XDA

A new firmware update for Sony's latest Xperia Z5 and its compact variant is making its way through several regions. The new firmware bearing build version number 32.0.A.6.152 is based on Android 5.1.1, the Android version the Xperia Z5 duo were shipped with. The update is currently live for the Xperia Z5 E6653, Z5 Dual models E6633 and E6683 and Z5 Compact models E5803 and E5823. Sony has already revealed the list of devices for which it will release upgrades as well as seeded AOSP Marshmallow binaries.

The camera app becomes quite fast with the update, and the messaging app no longer causes lags. You should also notice updated Home versions, re-optimised phone heating issue, RAM and Calendar optimisation, fingerprint scanner improvements and shutter function.

Most importantly, this build patches the notorious Stagefright security exploit, confirm folks on the XDA forum. Older Xperia models such as Xperia Z3, Z3 Compact and Z2 series have already received the Stagefright bug fix.

So if you have a brand new Z5 or Z5 Compact, update your devices as soon as possible to get rid of the Android vulnerability that could allow hackers to get media privileges of your device when processing an MMS, without any need of end-user action. To grab the update manually, go to Settings>> About phone>> Software updates>> System updates. The FTF files are also available, which you can install manually on your phone using Sony flash tool.

FTF files

Xperia Z5 E6653

Xperia Z5 Dual E6683 (or from here)

More about Stagefright fix
Sony