Select Cistercian abbots were permitted to administer major Holy Orders

The privilege was limited to ordaining deacons (not priests)

Cistercian abbots were permitted to ordain their confreres to the diaconate in the 15th century, but not to the priesthood. The practice began in 1400 (Pope Boniface IX allowed it) and was confirmed in 1427 (Gerentes ad vos, Pope Martin V). The Abbot of Cîteaux and the four primary abbots were given this privilege, usually restricted to bishops. Abbots ordained, albeit sparingly, until the seventeenth century. In a recent article, the best treatment of the topic to date, Troupeau lists less than 15 documented incidents and includes facts about who ordained, where, and when. This privilege was also given to other powerful monastic and canonical prelates.
​It is to be understood, so argues Troupeau, in the context of "the Great Western Schism." Popes sought to bind influential orders more strongly to the Apostolic See, and also to keep aspirants to Holy Orders close to their abbey and away from decadent university towns. Finally, there is an argument in the theology of the sacraments concerning the difference between priestly ordination (which the prelates had) and episcopal ordination (which some consider only a marginal increase in gradation). Therefore, what might seem at first like a decadent practice actually sprang from the will to reform.
Jean Troupeau, Le privilège des abbés cisterciens d'ordonner aux ordres majeurs: son origine, sa mise en oeuvre et son extinction. Cîteaux 74 (2023) 277-320.