God may act through others for purposes unknown, but it seems clear that Jesus must still be the center of the action.
Mark 9:38"Teacher," said John, "we saw a man driving out demons in your name and we told him to stop, because he was not one of us.“
39"Do not stop him,” Jesus said. "No one who does a miracle in my name can in the next moment say anything bad about me,
Does that suggest someone without legitimate authority can perform a miracle?
And these signs will accompany those who believe: In my name they will drive out demons; they will speak in new tongues;
We are reminded:
He called his twelve disciples to him and gave them authority to drive out evil spirits and to heal every disease and sickness.
Then Jesus came to them and said, "All authority in heaven and on earth has been given to me.
If you forgive anyone his sins, they are forgiven; if you do not forgive them, they are not forgiven."
For me, if a miracle was performed/claimed by someone outside of the legitimate authority of Christ I would have to evaluate the conditions and purpose of the miracle. I do not know of any. The truth of a miracle is only for Gods glorification in my view.
We are cautioned:
For many will come in my name, claiming, 'I am the Christ, ’ and will deceive many