From a recent Washington Bezos exclusive:
Prospective jurors in [Roger] Stone’s trial had completed confidential questionnaires that asked for their views on Trump, Stone and others caught up in Mueller’s investigation. Stone’s lawyers agreed to keep the responses confidential, and no details had been disclosed publicly. Questionnaires completed by those selected as jurors were later leaked to right-wing operatives, prompting an FBI investigation. No findings were ever publicly disclosed.