Laptop screen brightness changes as I play videos full screen

Hi
As I play any video full screen on my laptop (windows 10 pro 64-bit), the brightness of the screen changes to full bright, automatically. Exiting the full screen mode once again brings the screen light back to normal/last adjusted screen brightness. So, the problem is only in the full screen mode.
Does it have anything to do with K-lite media player classic? If yes, what could be the fix. I am using the latest codecs.
Thanks.

The brightness change most likely happens because the power plan changes. The player itself does not do that, but you should have a program on your laptop that does this based on what software is being used. Removing that program or changing its settings should solve it.