CNN provided Stone's lawyer with a PDF copy of the sealed indictment hours before the court was notified, even before he had heard from Stone, and hours before it was unsealed by the court. And the copy provided by CNN is identical to the filed version.
It was leaked by somebody with access.
The metadata indicates it was authored by "AAW" which appears to fit Andrew Weissmann of the counsel's office.
Someone should be prosecuted. Stone can’t prosecute but he can move for contempt and/or file a bar complaint.