Possible head gasket leak?

Hello everyone, I started doing an oil change today on my 2017 wrx and when I removed my oil cap there was a decent amount of coolant mixed oil waiting to greet me. The only reason I didn’t immediately jump to the obvious conclusion was because there is no white smoke, no sweet smell, no coolant in the oil I drained, no oil in my coolant, and no loss of power or over heating.

I know it’s probably the head gasket but does anyone else have any theories?

Thanks for any help