The source revealed itself.
Once that happens the reporter(s) can choose to maintain a silence, deny or confirm. The correct course was taken here by the confirmation.
"The family believes that my grandfather, Mark Felt Sr., is a great American hero who went well above and beyond the call of duty at much risk to himself to save his country from a horrible injustice," a family statement read by grandson Nick Jones said. "We all sincerely hope the country will see him this way as well."
NOW, HAND OVER THE MONEY TO MY FAMILY FOR OUR STORY.