Someone very dear to me had a few of these water stains on her ceiling. They’re quite an eyesore to me, and they’re not too hard to fix.
All it takes is one can of Covers Up by Zinsser. It’s an oil base paint and primer that can easily seal a water stain.
This was by far the worst of the bunch.
While it dried a little bit darker than the rest of the paint, it looks so much better now.