Mitrovic came off the bench to score the Magpies' third goal - his second inside a week.
But his suspect temperament let him down once again when he caught Lanzini in the face.
The incident was missed by match referee Neil Swarbrick but the Football Association reviewed footage, which was highlighted by Match of the Day and Sky Sports pundits afterwards.
The striker has subsequently been charged with violent conduct which could see him suspended for Newcastle's next three games.
He has until 6pm tomorrow to respond to the charge.
Mitrovic was red carded twice during his first season at St James' Park and his disciplinary problems have seen him used sparingly by manager Rafa Benitez.
Ironically, just minutes after the final whistle on Saturday, the former Anderlecht hitman talked of his frustrations at not been trusted "by certain people," and his determination to improve his image.
A ban would see Mitrovic miss Premier League games against Swansea, Stoke and Liverpool.
And this latest controversy comes at a time when it has emerged Newcastle are ready to listen to offers for fellow striker Dwight Gayle.
Mitrovic has been told he is staying put, despite strong interest from the Continent but if Benitez is successful in signing another striker before Thursday's transfer deadline, he will almost certainly slip down the pecking order at Newcastle.
He has yet to start any league game this season with recent buy Joselu preferred to the axed Gayle against the Hammers.
