Does inserting a finger with ointment into the anus of a fasting person break the fast? If so, is it excused if it happens unintentionally?

Inserting a finger into the anus invalidates the fast and necessitates making up the day, according to the majority of scholars, unless the fasting person did so forgetfully, in which case their fast is not invalidated by it. The same applies to all other things that break the fast if done forgetfully.