This isn't a great video of it, since my iPhone adjusts the exposure as the brightness changes.  But you can see as I scroll the brightness changes.

It doesn't happen only with ARFcom, although it doesn't happen with every website.  I tried a monitor reset.  Didn't help.

If I have an app like Excel windowed, only the browser window changes brightness when I scroll through it.

Laptop has Intel HD GPU with Max-Q RTX 1060.  HDR is on.



UPDATE 12/29/20:  I turned HDR off in Windows, and the problem disappeared - hopefully for good.
I wonder if my monitor isn't handling HDR properly.

Could also be a weird dynamic contrast setting or potentially due to your display's local dimming going crazy with HDR.
I don't think too many PC displays have local dimming though.

Edit- Apparently, Windows has an auto-brightness setting on by default. Also, laptops usually have power/performance settings that could potentially do something similar.