Download latest Android Lollipop 5.1.1 stock firmware for M8S TV Box from here or here. Download latest Android KitKat 4.4.2 stock firmware for M8S TV Box from here. Download previous firmware from here.
Model: M8S TV Box
Image file size: 475MB
Platform: Amlogic S812
Build number: Android/n200C/n200C:5.1.1/LMY47V/20160721:user/test-keys
Inside archive: firmware + aml_autoscript + factory_update_param.aml + recovery.img + u-boot.bin
Caution: Please do not update firmware unless you know what you are doing, you really want it or it is absolutely necessary. Firmware updates may occasionally have bad results, like bricking your device, temporarily or permanently. The firmware update process is done entirely at your own risk. Before attempting to update the firmware, back up your data.