Jon Daly started the move when he played the ball out to Andy Welsh on the right touchline. The winger skipped past Kerry Mayo and raced clear before pulling the ball across goal to the far post where Wilbraham had a simple tap in.
It was no more than the Hatters deserved after a terrific second-half performance caused the promotion-favourites all sorts of problems.
But McIlroy's men had to thank James Spencer for a wonderful 58th minutes save. The 18-year-old, recalled in place of Nick Colgan, somehow kept out Chris McPhee's 18-yard drive that was heading for the top corner.
Brighton had the better of things in the first period but failed to really trouble Spencer thanks largely to sterling defensive work from Rob Clare, Martin Pemberton, John Hardiker and debut-boy Matt Heath.
County were much more offensive after the break and had two golden opportunities to take the lead in the opening seven minutes.
First Owen Morrison saw a shot tipped over then Jon Daly failed to capitalise when Michel Kuipers dropped the ball at his feet. Daly got his shot away but it lacked powered which enabled a home defender to clear off the line.
Rickie Lambert came close with a 25-yard drive on 63 minutes as the Hatters continued to press.
Five minutes before the goal Welsh again caused havoc with a 40-yard run deep into the box. He pulled the ball back to Wilbraham who decided to dummy rather than shoot. Unfortunately the ball ran straight to Guy Butters who was able to clear.
Wilbraham forced another save from Kuipers 3 minutes from time as the visitors continued to confound their lowly position.
And from the next attack Morrison burst clear but failed to pick out Wilbraham who had pulled away from his marker.
With the travelling army celebrating victory the Seagulls almost grabbed an unlikely, and undeserved equaliser, deep into stoppage time but Richard Carpenter's drive was deflected wide.
County (4-4-2): Spencer; Clare, Heath, Hardiker, Pemberton; Morrison, Goodwin, Lambert, Welsh; Daly (Barlow 89), Wilbraham.
Subs not used: Challinor, Colgan, Jones, Lescott.
