Perhaps the Prince of this world will seek to cast doubts on Christian fervor and God's graces and miracles.
That's a good question, and a better rebuttal than the rationalistic attempts to explain away the phenomena. Keep in mind:
Matthew 12:25-27 If Satan drives out Satan, he is divided against himself. How then can his kingdom stand?
So the question is, does good fruit come from this miracle? If so, then Satan would be "driving out Satan." This is one criteria used by the Church to determine the authenticity of a miracle. The other criteria is to determine whether any teaching associated with the phenomena contradicts public revelation. If so, then the phenomena would not be from God. Because God cannot contradict Himself.