If and When a Catholic Priest May Reveal Something from a Penitent's Confession

This question is motivated by one of the answers given [here](https://law.stackexchange.com/a/93770/24981) for the question [Is religious confession legally privileged](https://law.stackexchange.com/questions/93765/is-religious-confession-legally-privileged) . I am under the impression, correct me if I am wrong, that if a Catholic priest reveals anything that was told to him during Sacramental Confession---he is automatically excommunicated by the Church. QUESTION: If the penitent involved gives permission for that priest to reveal something from his confession, may the priest do so without ecclesiastical penalty? Or is he still bound to reveal nothing?