It is possible that hypocrites are present when the absolution is pronounced, for a pastor cannot see into a person’s heart. God alone knows them. But a hypocrite does not receive forgiveness for himself, because he does not through faith accept the grace offered and pronounced to him. The absolution is not automatically effective without faith.
Heb. 4:2: Unto us was the Gospel preached, as well as unto them; but the word preached did not profit them, not being mixed with faith in them that heard it.
Is. 62:10: Let favour be showed to the wicked, yet will he not learn righteousness; in the land of uprightness will he deal unjustly, and will not behold the majesty of the Lord.