or hot mike
a microphone that is actively recording or broadcasting, especially if it captures a comment or conversation that the speaker or speakers believed to be private (often used attributively): The techs should limit the number of hot mics to reduce acoustic feedback. The reporter was suspended after her profanity was caught on a hot mic. Their hot mic scheming confirmed the conspiracy theories.
Origin of hot mic
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019