Ole Gunnar Solskjaer’s side picked up all three points in a chaotic game on the south coast, which was filled with plenty of VAR controversy.
Brighton went 1-0 up on the 40-minute mark after Bruno Fernandes’ challenge on Tariq Lamptey drew a penalty, which Neal Maupay audaciously converted with a panenka.
The Red Devils drew level before half-time, with Lewis Dunk steering into his own net after a Nemanja Matic cut-back.
With the game at 1-1 in the second half, Brighton’s Aaron Connolly was adjudged to have been fouled by Paul Pogba in the United box and the referee initially pointed to the spot.
However, after being advised by the VAR to check his monitor, Kavanagh reversed his decision, which could have swung the game in the Seagulls’ favour.
Commenting on the decision, United legend Ferdinand told BT Sport: ‘I just believe that’s a penalty.
‘Pogba was in the wrong position, panicking, I know exactly what it’s like to be in that position, trying to do all you can to get your body back in the right position.
‘There is a coming together and there’s enough contact there to go down.’
Ole Gunnar Solskjaer’s side’s last opportunity to score was seemingly scorned as Harry Maguire’s goalbound effort was cleared off the line by March.
However, after the referee blew his full-time whistle, VAR was once again involved as play was brought back for a handball by Neal Maupay in the box.
United were awarded a penalty, which spot-kick expert Fernandes duly converted to give the Manchester club their first win of the season, in the most dramatic fashion.