Vyvyan Basterd
Adventurer
I can't judge whether you're overreacting. I don't agree with all the "DM Approval" replies so far, I think it is more of a group decision (obviously talking about the person here, not their character). Does the game take place in your home? As wedgeski said it would be rude to invite someone without asking. Did you tell your players you were looking for more? If so, I'd be careful to not jump too hard on the gung-ho player who found you another. Do you trust the person who invited the new player? This would be big to me. If a relative newbie to the group invited someone to my home, I wouldn't be happy about that. But I'll trust a friend not to bring someone obnoxious and I'll agree to invite them into my home without meeting them. But, my friends have always asked, not told me, that they would like to invite new players to my home.