Veteran striker Jamie Cureton's 20th goal of the season helped Exeter defeat promotion rivals Northampton.
Exeter took the lead when Cobblers keeper Lee Nicholls fumbled Craig Woodman's corner into his own net.
Nicholls denied Cureton when he was clean through before Arron Davies missed an open goal following another error from the keeper.
Cureton, 37, glanced home Matt Oakley's free-kick and Jake Gosling's shot eluded Nicholls for the third.
The Cobblers, who saw Adebayo Akinfenwa and Clive Platt efforts cleared off the line, drop a place in League Two with Exeter rising above them to fourth, a point off the automatic promotion places.