Why does my second monitor bleed through the capture in window capture

[Sharkee]

There are times when second monitor bleeds through the capture scene, or even other applications bleeding through the capture scene.

I'm using window capture mode (Firefox) and it's maximized and I've reset transform.

https://i.imgur.com/80EDfTI.png

https://i.imgur.com/SD3aXbe.png

Please help me fix this! Thanks very much!