I believe that one of the major developments in the Magisterium of the Church under Pope Francis is in the area of the sin of self-righteousness, a major theme across many of his homilies, also his encyclicals and other documents of the Magisterium. The Catechism of the Catholic Church is silent about this sin, but the recent spate of Pope Francis homilies have been focusing on the theme of self-righteousness, or "accusing others" as he calls it. I started to notice Francis picking up this theme on September 6 (https://www.vaticannews.va/en/pope-francis/mass-casa-santa-marta/2018-09/pope-francis-homily-daily-mass-accuse-oneself-not-others.html) when he taught that the Christian way is to accuse ourselves, not others.
But, it is his Sunday homily on September 10 (https://www.vaticannews.va/en/pope-francis/mass-casa-santa-marta/2018-09/pope-francis-homily-daily-mass-newness-gospel.html) where he starts shaking the ground. The First Reading is the part of I Corinthians 5 where Paul is admonishing the Church of Corinth to root out sexual immorality. The Pope picks up on this theme with his term "novelties." For Francis, the "novelty" is the idea that we we have evolved beyond some primitive early church morality. I think he is thinking of the idea of many Catholics and even some priests and bishops that a person can live a homosexual lifestyle as a Christian, because "today, it can be done this way." The Pope clearly states, "There is a distinction between the 'newness' of Jesus Christ, and the 'novelties' that the world proposes to us as a way of living." Notice, however, that the Pope does not name any names. He is following his own advice from the earlier homily and he is not accusing anyone. Another fascinating aspect of the same homily is the allowance of Pope Francis for the sin of weakness, which he clearly distinguishes from the hypocrisy of someone who claims to be a Christian but lives out the "novelties." At the end of this homily, Pope Francis brings up the theme of the next homily: the great accuser, Satan who accuses the people of God of their sins.
Notice how Francis successfully walks the tightrope between liberty and law. I have never read a Pope accomplish this as successfully as Pope Francis does. As much as I love John Paul II and Benedict XVI, they tended to focus on the moral teachings without warning against the risk of self-righteousness. Francis upholds the moral teachings of Jesus and the Church while simultaneously calling out self-righteousness.
In is his homily on Monday, September 11 (https://www.vaticannews.va/en/pope-francis/mass-casa-santa-marta/2018-09/pope-francis-mass-great-accuser-bishops-scandal.html), Pope Francis says that the "Great Accuser," Satan, is attacking bishops of the Catholic Church to create scandal. This is an incorporation into the Magisterium of the Catholic Church the basic Evangelical (and Scriptural) understanding of the role of the Accuser of the Brethren. When Satan accuses us of our sins, our response must be, before God, to accuse ourselves of our sins in agreement with Satan, and then to thank Jesus for shedding his Blood of the Cross for the forgiveness of our sins. My own opinion is that Pope Francis has Vigano in mind, who accused a ton of bishops in his 11 paged "Testimony" (http://www.ncregister.com/daily-news/ex-nuncio-accuses-pope-francis-of-failing-to-act-on-mccarricks-abuse).
In his next homily on Tuesday, September 12 (https://www.vaticannews.va/en/pope-francis/mass-casa-santa-marta/2018-09/pope-francis-at-mass-mercy-is-the-christian-style.html), the Pope points out that when we participate in this accusation process, we are actually entering into Satan's logic. Again, I think he is homing in on Vigano, but the Pope -- a better man than I am -- actually refrains from accusing Vigano of self-righteousness, again following his own homiletic advice. Pope Francis is silencing himself and he is refusing to enter into the logic of the Accuser of the Brethren.
It is obvious to me that the Pope is deeply troubled by the sin of self-righteousness, more than he is on fitting into the American news cycle, which interprets his homilies in light of the top stories of the hour. He has even risked the misinterpretation of his words as an attempt to silence sex abuse victims from accusing abusers. A future Pope, if not Francis himself, may incorporate this development of doctrine of the sin of self-righteousness into a future update to the Catechism of the Catholic Church. I love that our Pope is not trying to please any American political discourse. By focusing on the Gospel of Jesus Christ, this Pope is rejected by both ideological political spectrums. He does not fear any man. He is preaching the Word of God. "He who has ears, let him hear!" (Matthew 11:15)