Roommate left skid marks in my toilet whilst I was away?

I live with a roommate. We both have our own toilets, mine being downstairs, his is in his ensuite. I was away for a few weeks, and when I get back I saw skid marks in the toilet. He had clearly used it and it was gross.

should I bring this up to him?

Roommate left skid marks in my toilet whilst I was away?
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