X3 Can anyone possiblely identify this for me?

[EmmaRobert]

To all the experienced bimmer family members-

Have you seen anything like this before? I have a 2017 x3, never use the armrest/cup holder in the back. Please see pics, it looks like frost but it is not cold.

I did not drive it very often the first year, and it mostly parked outside during winter and summer. Start driving it on a daily basis since this year, and park it in the garage most of the time.

[Auto Parts Guy]

Looks like mold or some type of fungus.