Download Android KitKat 4.4.2 stock firmware for MK903V TV Stick from here or from here.
Download a previous firmware version from here.
Firmware details
Firmware: MK903V RK3288 Android 4.4 TV Dongle Firmware 176187 150707
Firmware file name: update_TV10_ap6330_2015_04_20.img
Model: MK903V TV Stick
Image file size: 392 MB
Platform: Rockchip RK3288
Boot version: 2.17
FW version: 4.4.02
Build number: rk3288-eng 4.4.2 KOT49H eng.root.20141227.103800 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.