The return of some fans at Brighton for the first time since February saw them go ahead with a well-taken first half penalty from Pascal Gross.
A towering header from Vestergaard from a James Ward-Prowse corner pulled the Saints level and Danny Ings' second half spot kick ensured the Saints secured all three points.
It was tough on Brighton and their fans as VAR ruled that Solly March's 80th minute challenge on Kyle-Walker-Peters was inside the box.
Ings, in his first game back from a knee injury, showed little sympathy and sent Maty Ryan the wrong way from the spot.
Scroll down and click through to see how the players rated.
5. Tariq Lamptey 6/10
Back after a one match ban and a lively presence as always on the right. Didn't quite have the impact in the final third as he has in previous matches
6. Ben White 6/10
Alongside Bissouma in defensive midfield. Covered plenty of ground and constantly aware of danger, going with runners and making blocks. Neat and tidy in possession. Subbed on 81 for Jahanbakhsh
7. Yves Bissouma 7/10
Another high energy and competitive display from Bissouma. Good with the ball and always looked to drive Albion forward from deep. Looked frustrated and Booked for late foul on JWP
8. Pascal Gross 6/10
Kept his composure once again from the spot. Displayed a good range of passing throughout the 90 minutes. Fired a shot over when well placed on 66 minutes. Booked for protesting against the late penalty