During the meeting, the Board of Governors voted to allow NFL-style challenges from head coaches in games next season. The Athletic's Shams Charania first reported that development.
Sacramento Kings owner Vivek Ranadive expressed concern that the vote was being reported on while the meeting was still in session, according to MacMahon. Cuban then reportedly admitted to leaking the information.
Shortly afterward, the NBA officially announced the changes to the instant-replay rules.
"I appreciate the irony of your reporting on a fine that someone should, but won't, get fined for leaking to you," Cuban told ESPN.
The NBA has fined Cuban more than $2 million since he took ownership of the Mavericks in 2000.