Leyton Orient's eight-match winning streak was ended by an excellent away victory for struggling Scunthorpe.
Full-back Christian Ribeiro put the visitors in front, receiving a pass from Mark Duffy to slot through the legs of Orient keeper Ryan Allsop.
Karl Hawley converted Duffy's free-kick to double the lead, before Kevin Lisbie brought it back to 2-1 from the spot after Ribeiro's handball.
But Damien Mozika made the game safe, his shot deflecting past Allsop.
VIEW FROM THE DRESSING ROOM
Leyton Orient manager Russell Slade told BBC London 94.9:
"It was a below-par performance from us today and that was a little bit disappointing.
"In previous games we've had any amount of players in really good form.
"Today, we were struggling to find even one or two players in form. The biggest thing is the way we conceded all three goals."
Scunthorpe United boss Brian Laws told BBC Radio Humberside:
"This wasn't an easy game and I think when you look on paper - a team that's won eight on the bounce, this was going to be a difficult game.
"I thought the start was important. I don't think Steve Mildenhall had a shot to save in the first half, which was important for us to build on.
"In the second half I said, 'even if we can improve by 10 per cent we'll go on and win'."