How do I stop my white background from becoming grey due to lighting? I'm trying to make a 3D rendered shot of my product model. I want the background to be plain white.
However, when I use a plain without material, it's greyish, depending on the lighting. If I use a material on the plane, there are artifacts/fireflies on my product model.

What's the best approach to solve this problem?
"it's greyish, depending on the lighting".
Indeed the solution is exactly in that statement. Use brighter sources and the "gray" can look like white.

Just increase the "power" of the lamps, or use a higher number than 1 on the strength (if you are using nodes)