Gwyneth Paltrow has come out swinging against rumors that she's cheating on hubby Chris Martin.

A message about Gwyn appeared on Whisper — an anonymous secret-sharing app — earlier this week, claiming that she's been having an affair with entertainment lawyer Kevin Yorn, according to Gawker's gossip blog Defamer.

Her rep then issued a statement to Defamer calling the Whisper posting "100-percent false" and insisting that "this is clearly a fabricated story with no credibility at all...  I cannot be more clear with you when I say she is NOT having an affair with Kevin Yorn, and I will be notifying her attorneys as well."

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