Fn button works without pressing it?

I recently formatted my Lenovo Y700 and I'm facing a strange problem. On my laptop, for example, you can change the light intensity with the up and down arrows. Before that, I had to use the Fn key to change this setting. But now this setting works without using the Fn key. Now that I can use these arrows "normally", I have to use the Fn key. Does anyone know how I can change this setting?

Either that's because of an update, or (more likely) because of ghosting. So that your keyboard recognizes inputs that you do not enter. Can also be something else.