The Atlantic’s top editor said he was added to a text group in which top US officials discussed plans to bomb the Houthi militia in Yemen, an extraordinary breach of security from an administration that has repeatedly vowed to clamp down on leaks.

Atlantic Editor-in-Chief Jeffrey Goldberg recounted in a 3,500-word story published Monday how he got a connection request on the Signal messaging app from someone identified as Michael Waltz. He initially believed the request was fake, but came to realize the account belonging to the US national security adviser was genuine after the group discussed detailed — and possibly classified — plans for an attack on the Houthis.