Hull climbed out of the bottom three of the Premier League for the first time since October and pushed Middlesbrough closer to relegation with a vital 4-2 home win on Wednesday.
Marco Silva's side trailed to Alvaro Negredo's opener, but Lazar Markovic equalised before Oumar Niasse and Abel Hernandez put Hull in control at the KCOM Stadium.
Middlesbrough's Marten De Roon got one back just before half time, but Harry Maguire headed Hull's fourth midway through the second period.
The Tigers' fifth win in six home league games lifted them two points above Swansea, while Middlesbrough, without a league win since December 17, are seven points from safety and appear destined for a return to the Championship.
Hull thought they had drawn first blood but Niasse was deemed offside when he turned the ball home at the end of a slick move in the third minute.
The first blow was landed by Middlesbrough two minutes later.
Adama Traore's low angled cross from the right side of the penalty area was turned home at the far by the unmarked Negredo.
It was the Spaniard's first goal since the end of January and only the visitors' second in seven league matches.
The Tigers equalised in the 14th minute through Markovic, who slammed the ball home from close range after the visitors had failed to clear Niasse's flick-on from Andrew Robertson's cross.
Hull turned the game on its head in the 27th minute.
Alfred N'Diaye hooked the ball forward and Hernandez's headed pass fell invitingly to Niasse, who buried his shot under Victor Valdes from 12 yards.
Hull struck again when Maguire's diagonal ball was crossed first time by Kamil Grosicki from the right and with Valdes stranded, Hernandez steered home his fourth league goal of the season.
Middlesbrough reduced the deficit in first-half stoppage time in controversial circumstances.
Adam Clayton's corner was nodded on by Ben Gibson and with both De Roon and Traore clearly offside, the former headed home.
Referee Michael Oliver consulted with his assistant and to the disbelief of Hull's players and fans he allowed the goal to stand.
But Hull gave themselves some much-needed breathing space and restored their two-goal cushion in the 70th minute when Maguire stole in unmarked at the far post to head home Robertson's curling cross.