See here the witness of Pope Paul IV in his Bull Against Heretics where he acknowledges the danger of a false prophet Pope.

“§1. We considering a matter of this kind to be of so grave and perilous a nature that even the Roman Pontiff, who is the viceregent of God and the Lord Jesus Christ upon earth, having a plenitude of power over nations and kingdoms, judging all and being judged of none in this present world, may nevertheless be reproved if he is found deviating from the faith-and (considering moreover) that where there is greater danger there should be also a fuller and more diligent consultation, lest false prophets or others having secular jurisdiction also, should entangle miserably the souls of the faithful, and should draw down with them into perdition and destruction the innumerable peoples committed to their charge and government in spiritual or temporal matters, and so it might happen that we should see the abomination of desolation spoken of by Daniel the Prophet, in the holy place.”

Cum_Ex_Apostolatus_Officio

Recall that Daniel the Prophet was the one who received the Book of Truth and sealed it up until the end time (see “Contained in Public Revelation” in our Encouragement section).