Perry Ng scored the winner as Cardiff beat QPR 2-1 to increase the west London 'relegation worries.
Paul Smyth equalised for the hosts to cancel out Dimitrios Goutas' opener, but Rangers' defensive shortcomings were badly exposed again.
They remain in the relegation zone and are without a win in five matches - a run which has included four defeats.
A lack of goals has been a huge problem for them - they have scored just twice in their past six games and have managed just 21 in the league this season.
So the last thing they needed for the first of four consecutive home league matches during January was to be without playmakers Ilias Chair and Chris Willock.
Both missed the game, with talisman Chair having gone off injured during the second half of Friday's goalless draw at Ipswich, where Willock was replaced at half-time amid ongoing issues with his fitness.
QPR could also ill-afford to continue their habit of conceding sloppy goals from set-pieces.
But that is exactly what happened, with Goutas able to head in Joe Ralls' 16th-minute corner for the opener.
The only effort on target that the home side managed during the first half was a tame free-kick from Kenneth Paal, which was comfortably dealt with by goalkeeper Jak Alnwick.
But Northern Ireland forward Smyth hauled them level seven minutes after the interval with his second goal of the season.
Youngster Rayan Kolli, on as a half-time substitute, retrieved the ball after Sam Field's effort had been blocked and he whipped in a cross towards Smyth, who slid in to score at the far post.
However, another goal from a set-piece resulted in Cardiff retaking the lead with 16 minutes remaining. Keeper Asmir Begovic failed to deal with Ryan Wintle's corner and Ng was on hand to score with a free header.
It clinched the second win in as many away matches for the Bluebirds and lifted them to ninth in the table, just three points adrift of the play-off places.
QPR, meanwhile, have improved since Marti Cifuentes replaced Gareth Ainsworth as boss, having recently won three games in a row, but they clearly have problems at both ends of the pitch.
Smyth scored with a piece of opportunism, but they otherwise offered very little in attack and always seemed defensively vulnerable.
They rarely looked like finding another equaliser after Ng's goal, although Alnwick was called upon to produce a late save to deny Sinclair Armstrong.
QPR: Begović ©, Dunne, Clarke-Salter (Fox 81’), Field, Dykes, Smyth, Dozzell, Dixon-Bonner (Adomah 67’), Cannon, Larkeche (Kolli 46’, Armstrong 81’), Paal. Subs not used: Archer, Kakay, Talla, Drewe, Pedder.
Cardiff City: Alnwick, Ng, McGuinness, Goutas, Collins (Panzo 87’), Siopis (Adams 87’), Wintle, Ralls ©, Méïté, R. Colwill (Tanner 74’), Etete (Bowler 60’). Subs not used: Turner, J. Colwill, Evans, Ugbo, Robinson.