Weird Stain on Interior Arm Rest

[Dathaeus]

39706

I had a little discoloration before but after the last car wash, I think it got worse.

What is this weird white stain and what is the safest way to thoroughly clean these marks on this surface, is there a professional product I can buy?

[John in VA]

Use a diluted all-purpose cleaner to get it really clean before using any vinyl/rubber/leather treatments.
https://www.theartofcleanliness.com/automotive/best-all-purpose-cleaners-car-detailing/