Download Android KitKat 4.4.2 stock firmware for MK903V TV Stick from here or from here. Download a previous firmware version from here. Download Lollipop 5.1.1 firmware version from here. Download Rockchip Driver Assistant v4.4 from here and download Rockchip Batch Tool v1.8 from here.
Firmware file name: update.img
Model： MK903V TV Stick
Image file size: 269 MB
Platform: Rockchip RK3288 / RK32
Boot version: 2.17
FW version: 4.4.02
Build number: rk3288-eng 4.4.2 KOT49H eng.root.20160406.181008 test-keys
Model number: MK903V
SDK version: RK30_ANDROID$(PLATFORM_VERSION)-SDK-v1.00.00 \
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.