My Cat Which Is Well Litter Box Trained, Pooped In

My cat which is well litter box trained, pooped in a corner on the carpet today. It was soft and I noticed what looks like a spot of dark blood about the size of a dime. She is 7 years old and has never gone outside of her box. I have only had her for 9 months, but she has never done this before. Unfortunately I did feed her some rotten cat food yesterday which she vomited up about 10 minutes later. She also is not a vomitter.