There could be several reasons why a cat might suddenly poop inappropriately. Here are some common possibilities:
1. Unclean litter box: If the litter box is not cleaned in time, there will be too much feces and urine inside. Cats with a strong aversion to cleanliness may not want to relieve themselves there and will consider going to another place.
2. Litter box location: If the cat's litter box is in a noisy area, the cat will feel unsafe and uncomfortable and won't use it. Placing the litter box in a quiet corner will encourage the cat to use it on its own.

3. Cat is sick: When a cat has an upset stomach, diarrhea, or constipation, it may defecate indiscriminately. In this case, you need to take the cat to the vet immediately, clean up the feces, and thoroughly disinfect the area.
4. Anxiety: Cats may feel neglected due to their owner's prolonged absence, being scolded or beaten, the arrival of another pet, fright, or stress reactions. These factors can trigger a series of strange behaviors, such as urinating indiscriminately, biting, meowing, and scratching.