STOCK FIRMWARE
CUBE 3 flashable STOCK FIRMWARE (click image to download)
HOW TO ROOT STOCK - CUBIX CUBE 3
backup stockrom;
goto advanced wipe: system, data, cache, dalvik/art cache
then do a full wipe except internal and external storage.
then restore your backed up stockrom.
reboot to system,
then reboot to recovery and flash supersu.
you have to follow above steps so that supersu will be installed successfully.