If you own an old Xperia Z device, then you should know that the Android 5.1.1 Lollipop update has started rolling out to these devices. According to Xperia Blog, the Android 5.1.1 Lollipop update is available for the following devices: Xperia Z, Xperia ZL, Xperia ZR and Xperia Tablet Z (both LTE and Wi-Fi).
Unfortunately, the Android 5.1.1 Lollipop update has the build number 10.7.A.0.222 and it doesn’t include the patch for the Stagefright exploit. The Android 5.1.1 Lollipop is not a major update for the Xperia Z, Xperia ZL, Xperia ZR and Xperia Tablet Z, as the Android 5.1.1 Lollipop contains only bug fixes and improvements. However, since the devices will be updated from the Android 5.0 Lollipop to Android 5.1.1 Lollipop, it means that some new features will pop out here and there.
Likewise other software update, the new Android 5.1.1 Lollipop is released gradually, which means that depending on your region and carrier, your device will receive the update sooner or later. You can also manually check if there are new updates for your device, by going to Settings->About device->System Updates->Check for update.
HINT: If your device is not running an official Android build, you will *NOT* receive the Android 5.1.1 Lollipop OTA update.
Once you see that the update is available for your device, we suggest you to connect to a Wi-Fi network (to not waste the data plan from your carrier) and make sure that your device has 50% or more battery (to be sure that it will not shut down in the middle of the update).
Android 5.1.1 Lollipop for Xperia Z1, Xperia Z1 Compact, Xperia Z2, Xperia Z2 Tablet and Xperia Z Ultra
The same blog said that the Android 5.1.1 Lollipop will be released for Xperia Z1, Xperia Z1 Compact, Xperia Z2, Xperia Z2 Tablet and Xperia Z Ultra.
However, this update will come with the fix for the StageFright exploit. The StageFright is a dangerous exploit that will allow hackers to get access to your device with ease. All they need to do is to send you a MMS containing the virus. Once the device is infected, the hacker will have full access to it and he will be able to steal your personal information.
According to rumors, the Xperia Z, Xperia Z1, Xperia Z2 and Xperia Z2 Tablet variants will receive the Android 6.0 Marshmallow after it will get released. However, it is not yet known if these devices will receive the new Android OS before the end of 2015 or after.