Former Charlton trainee Stacy Long scored to end his old club's unbeaten record in npower League One as Stevenage upset the leaders.
Charlton had come through 12 league matches without losing, but Long, who failed to make the breakthrough at The Valley before leaving at the age of 20 six years ago, condemned them to a first defeat with his 11th-minute strike at the Lamex Stadium.
It earned Stevenage a 1-0 home victory and saw Charlton's lead at the top trimmed to one point, with Huddersfield climbing a place into second after a 4-0 win at Exeter, aided by a hat-trick from Jordan Rhodes.
Sheffield Wednesday will join Charlton on 28 points at the top if they beat Sheffield United in the derby at Bramall Lane on Sunday.
Huddersfield are now the only team yet to lose in League One, with Lee Clark's men unbeaten in 13 games this season and undefeated in 38 league games - outside the play-offs - since December 28.
They spared bottom-of-the-table Exeter no mercy at St James Park, where Alan Lee put the Terriers in front after eight minutes and Rhodes then took over the scoring.
The Scotland Under-21 striker netted after 26, 65 and 89 minutes, with the hat-trick clinching goal a close-range header, to give Huddersfield a convincing victory.
Notts County edged ahead of Wednesday to reach third place with a 3-1 win at Chesterfield.
Ben Burgess put County in front after 21 minutes and Alan Judge made it 2-0 by half-time. Craig Westcarr gave Chesterfield hope by netting in the 52nd minute, but Drew Talbot's late own goal restored the two-goal margin.