When a cat breaks litter box protocol -- unless it was unable to get to the box, eg by door being closed or another car deciding to guard it -- this is usually an indication of illness and time for a vet visit.

After that, treat the marked area with an enzyme based cleaner (available from pet stores under multiple brand names) to remove all traces of the scent, which might otherwise encourage a repetition.

When a cat breaks litter box protocol -- unless it was unable to get to the box, e.g. by a door being closed or another cat deciding to guard it -- this is usually an indication of illness and time for a vet visit.

After that, treat the marked area with an enzyme-based cleaner (available from pet stores under multiple brand names) to remove all traces of the scent, which might otherwise encourage a repetition.