Hi, glad to share the firmware for M8S+ TV BOX 

Download here: M8S+ AMLOGIC S812 FIRMWARE 

Flash method:

1, Select “File”-”Import image” to load burning image package
2, Select burning configuration, then click “Start”
3, Before close the tool, you need to pull out devices the click “Stop”

Please be noted, this firmware is fit for SD card upgrade.

You will find 4 file folders after unpacking ,  1 for Android 4.4 SD cared upgrade, 1 for  Android 4.4  PC upgrade, 1 for  Android 5.1  SD cared upgrade and 1 for  Android 5.1  PC upgrade, please check the image below:

Choose a suitable one for your device, Good luck!