Firmware can be used to update your TV Box device. However, please note that firmware is usually suitable to a specific hardware platform, and if you use it on another non-compatible device of TV box, you may brick your device. Here are the most popular TV Boxes in the market: Amlogic TV Box, Rockchip TV Box, Allwinner TV Box. The methods of using firmware on these boxes are different: Check HERE.
Click to find firmware and guide.
You can find more information about the models here:
For NEXBOX A95X (S905X CPU)
For NEXBOX A5 (S905X CPU)
For NEXBOX A1 (S912 CPU)