keyboard lights up while playing webm with audio track

I'm not sure what's going on, but this QL extension causes my keyboard to light up. I have it on a short timeout so it will dim, but without touching anything (my screen is all the way dimmed as I'm listening to this interview) the keyboard lights up again, and only when playing this webm via this extension

I have no idea what could be causing this. Only one .webm file, or does it occur with others?