Download latest KitKat 4.4.2 stock firmware for EM8 / M8N / M8 TV Boxes from here or here. Download previous version of firmware from here. To flash firmware on this box from SD card read this article.
Model: EM8 / M8N / M8 TV Boxes
Image file size: 376 MB
Platform: Amlogic S802 quad core
Update file name: M8N-ota-20151029.zip
Build number: M8N-user 4.4.2 KOT49H 20150917 test-keys
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.