Deferred Lighting and linear color space

Hello everyone,

I was just wondering why when you are in deferred lighting and linear color space, dirty light artifacts appear.

Here are 2 screenshots :



Just for comparison, I post the same image with Forward rendering and linear color space.

Here the light projection on the plane is very clean.

Do you where does this effect come from and how to avoid it ?

Thanks all !!
Gamgie.