Stain on the ceiling

[George P.]

I completed the rental inspection yesterday and the tenant pointed at the stain on the ceiling (painted Sheetrock) in the bedroom on the second floor (2-story TH). It certainly wasn't there a year ago, but the tenant cannot remember when they saw it first time.

It has yellow borders, about 12 inches in diameter and is not soft or damp or moist (it was raining hard a few days ago). During the last few rains the tenant checked on the stain and said it was nor moist, neither increasing.
I am coming back do get in the attic and investigate.
Looking for suggestions on what to look f?r once up in the attic.
Thanks in advance