The seven sacraments · Question 2.4
“Does Confirmation have to come from a bishop — is it fake if a priest does it?”

Confirmation — a mission strengthened in the Holy Spirit
The Church's answer: In the Latin Church the bishop is the ordinary minister of Confirmation, which brings out clearly that the person confirmed is bound to the local church and to the apostolic Church. But in the cases laid down in canon law a priest too receives the authority to confirm validly — when an adult is baptized, for instance, or when he holds a special delegation.
If they press further: “Does the power of the Holy Spirit change with the minister?” — No. Where a sacrament is celebrated with legitimate authority and the correct rite, its grace does not grow or shrink according to how famous the minister is or how highly his character is rated.
In one sentence: “The bishop is the usual minister, but Confirmation by a priest the Church has authorized is a true sacrament too — and the grace belongs to the Holy Spirit.”