Footage has emerged of the incident that could land Kylian Mbappe a ban against Arsenal, with Carlo Ancelotti responding to the investigation into his players.

This week, UEFA have launched an investigation into allegations of indecent conduct by four Real Madrid players, namely Antonio Rudiger, Kylian Mbappe, Dani Ceballos, and Vinicius Junior.
Rudiger is accused of making a throat-slitting gesture towards the Atletico fans, and Ceballos allegedly made an offensive hand gesture.
As for Mbappe, the offending incident was caught on camera by one fan in the stands:

Carlo Ancelotti has responded to reports of UEFA’s investigation into his team, with 10 days to go until the first leg of the Champions League quarter-final against Arsenal.
“We believe everything was correct and we hope UEFA makes a decision, but we trust that everything will end well,” Ancelotti said.
“We are confident in UEFA’s verdict as the players had just celebrated, that’s it, we wait for verdict, but our players didn’t do anything wrong.”

Though a ban is possible, it’s not certain, given UEFA’s history with dealing with such gestures.
In 2019, Atletico Madrid coach Diego Simeone turned towards fans and grabbed his crotch in celebration against Juventus. The incident was caught on camera and Simeone was fined €20,000, but he didn’t receive a touchline ban.
Perhaps things could be different in the case of a player. Jude Bellingham was also fined and given a one-match suspended ban for his own crotch-grabbing gesture during Euro 2024 last year.
But neither Simeone nor Bellingham were given an actual suspension, only fines and potential future suspensions. A fine for Mbappe seems the most likely.