So here is what I am experiencing. My One Max is a week old but from day one I have noticed that while i am typing a text message or email screen brightness increases a bit as soon as I hit any key on screen. Sometime it happens sometime it doesn't. I have also noticed that it only happens wherever key pops up on keyboard e.g E, R, G, O etc etc or it happens when I am scrolling messages or any thing which is in Black and White contrast (May it be messages or a web page with different dark and light pictures/rich text)
Mine is a brand new Stock Phone. No unlocked bootloader, or S-Off or Custom ROM or something of that sort. Brightness is at around 30%-40% in settings. Phone CID is HTC__J15 (Arab CID and International version).
I don't think its an hardware problem but wanted to share it with you guys and find a reason as well as a solution to it.