Southampton ended West Ham's nine-match unbeaten run with a 3-2 win at the London Stadium to surge into the Championship top six despite starting the season with a four-point deduction.
Saints began the campaign with the points penalty after spying on opposition training sessions, which also cost them the chance of promotion in the play-off final last season.
Kuryu Matsuki, James Bree and Lewis Dobbin all struck before halftime for the visitors, who are now within three points of the automatic promotion places.
Kyle Walker-Peters and Tomas Soucek replied for the Hammers, but there were swathes of empty seats and boos by fulltime as they missed the chance to go top.
"This is a tough place to come, against a quality team, and we knew we needed to start strongly, so we worked on that all week," said Saints boss Tonda Eckert after his side went 2-0 up inside the opening 10 minutes.
"They made it tough for us in the second half, so it was important that we stayed brave to bring the result over the line."
Burnley sacked manager Nicky Hayen after just 14 games in charge following his side's 4-1 defeat at Lincoln, which left the Clarets in the relegation zone.
Relegated from the Premier League last season, former Club Brugge boss Hayen won just one of his 12 league matches in charge.
"Burnley Football Club has dismissed head coach Nicky Hayen with immediate effect," the club said in just a two-sentence statement.
"The board has taken the decision following a disappointing start to the Championship season."
Swansea's missed the chance to retake top spot after they were thrashed 5-0 by QPR at Loftus Road.
Richard Kone scored a hat-trick inside the first 15 minutes before Jimmy Dunne's double rounded off a remarkable scoreline that nudges Rangers into the play-off places.
Adam Armstrong scored the only goal as fourth-placed Wolves beat struggling Watford 1-0 to move within two points of the automatic promotion places.