Sony — Flashtool 0.9.18.6 |link|

It works by communicating with the device in (powered off with the volume-down button pressed while connecting USB). It can flash:

Choose your device and the firmware from the list. Under the pane, check "DATA," "CACHE," and "APPSLOG" if you want a clean install (this deletes your data). If you only want to update without losing data, leave these unchecked. Step 5: Connect Your Device Sony Flashtool 0.9.18.6