1. If one had made gheebah of someone and the person whose gheebah was made came to know of the gheebah, then in order for one’s taubah to be accepted, apart from seeking forgiveness from Allah Ta‘ala, it is necessary for one to seek forgiveness from the person as well.
However, if the person whose gheebah was made did not know of the gheebah, then one does not have to inform him of the gheebah and seek his forgiveness. Seeking forgiveness from Allah Ta‘ala is sufficient.