Goalkeeper Alberto Brignoli sealed the first ever Serie A point for newcomers Benevento to spoil Gennaro Gattuso's debut as AC Milan coach in a 2-2 draw that was greeted like a victory by the hosts.
In a desparate scramble on front of goal Brignoli headed in five minutes into injury time to give the side from outside Naples their first point in 15 games.
"Someone from the bench told me to go up, I went to jump and I closed my eyes," said Brignoli.
Giacomo Bonaventura had opened for Milan after 38 minutes at the Stadio Vigorito, before George Puscas pulled Benevento level five minutes after the break.
Nikola Kalinic got Milan back in front seven minutes later before Alessio Romagnoli was sent off for a second bookable offence leaving the visitors a man down for the final 15 minutes.
But in the final seconds of the game as Benevento looked set for their 15th straight defeat Brignoli jumped highest after a desperate last free kick to scenes of euphoria among the home crowd.
Former Milan midfielder Gattuso had taken over midweek after predecessor Vincenzo Montella was sacked as the former European giants sit seventh way below the Champions League ambitions of their new Chinese owners.
"We have to improve our form and mentality but I've nothing to hold against the players," said Gattuso.
"They gave everything when down to ten. We conceded a goal that hurt."
Benevento had surpassed Manchester United's 12-game losing start, a record established 87 years ago, on November 19.
Inter Milan -- now the only unbeaten team in Serie after leaders Napoli lost 1-0 to champions Juventus on Friday -- can claim the championship lead later Sunday when they host Chievo.