First of All, Welcome to my BLOG On this Thread, you will find the Original link to Download Lenovo Vibe X3 X3A40 Stock ROM Firmware from Google Drive. Lenovo Vibe X3 X3A40 Firmware Package comes in a zip package, which contains Flash File and Flash Tool and Driver with How-to Flash Manual.
Device Name: Lenovo Vibe X3 X3A40
Android Version: 5.1 Lollipop
Install via: SP Flash Tool
File Size: 2.0 GB
File Hosted: Google Drive
How to Flash Lenovo Vibe X3 X3A40 Stock Firmware
Step 1: Download & extract the Firmware on your computer.
Step 2: After extracting Firmware zip file you will find the Driver and Installation Instructions.
Step 3: Install Latest available USB Drivers (Just skip this Step if your Computer already have).
Step 4: Follow the instruction to flash the firmware your Lenovo smarthphone.
Download Lenovo Vibe X3 X3A40 Firmware Update