The Sacrament of Confirmation. It won't be valid if your Baptism isn't valid, and Holy Orders won't be valid if your Confirmation isn't valid.
My latest on LifeSite
The big story of the weekend came from the Archdiocese of Detroit. A certain Matthew Hood watched a video of his own baptism and realized that the officiant, a permanent deacon, had used an invalid formula: he had said ‘We baptize you’, not ‘I baptize you’. This was of special concern since Hood, now an adult, had been under the impression that he had been ordained a priest in 2017.
In some ways, the story is reassuring. It was a letter from the Congregation of the Doctrine of the Faith, under Pope Francis, insisting on the importance of these things, which set this chain of events into motion. The Archdiocese acted swiftly to have Hood properly baptized, confirmed, and ordained, and has done its best to reach other people baptized by the rogue deacon.
Two things remain worrying, however. One is that it is impossible to know how many other people are affected by invalid sacraments. The other is that many Catholic commentators seem not to care.