A fifth win in a row has taken Mjallby seven points clear at the top of the standings for the time being, with six Allsvenskan matches in Round 19 taking place tomorrow or on Monday.
Malmo, meanwhile, have seen their 11-match unbeaten run in all competitions come to an end, and have missed the chance to go third and could find themselves as low as sixth come the end of the round if other results go against them.
The timing of the match wasn't ideal for the hosts, coming in between the two legs of their UEFA Champions League Third Qualifying Round tie against Copenhagen.
But there was no indication their minds were elsewhere when Taha Ali thundered a volley towards goal in the opening minute, which Noel Tornqvist palmed away. That was the first of a flurry of chances for the hosts - the best of which fell to Busanello, but he could not keep his volley down from close range.
Having threatened little in the first half, Mjallby went and broke the deadlock five minutes after the break, and did so with a huge slice of fortune - Herman Johansson's shot from the edge of the area took a huge deflection off Pontus Jansson, wrongfooting Robin Olsen in the MFF goal.
The Hallevik side needed a helping hand for the second goal, too, which arrived eight minutes later. Elliot Stroud cut into the penalty area from the left wing and, despite a tight angle, took on a shot which caught out Olsen, as he let it squirm through his fingers.
Despite two quick setbacks, Malmo were still pushing to get back into the game, and that persistence was rewarded with 20 minutes to play when a fine team move resulted in Daniel Tristan Gudjohnsen holding the ball up inside the box and laying it off for Kenan Busuladzic to sidefoot home.
Inside the last eight minutes, the home side somehow failed to equalise when Stefano Holmquist's header was kept from crossing the line by a combination of Tornqvist and Axel Noren, before Gudjohnsen failed to force it in from a couple of yards out.
To rub salt in the wounds, Mjallby profited from another Malmo error to seal the win in added time - a cross from the left looked to have been dealt with, but an underhit backpass by Busuladzic allowed Viktor Gustafson to steal in and prod the ball past Olsen.
By the time Mjallby play again they would have passed three months without defeat, though Malmo remain the last team to take a point off Anders Torstensson's side in the reverse fixture at the end of June.
In Saturday's other match, Sirius gained a valuable three points away at Halmstad, winning 1-0 and moving to within a point of their opponents and three points clear of the bottom three.
The Uppsala side brought top scorer Robbie Ure on with 18 minutes to play, and it took the Scotsman just four minutes to make the decisive impact and score his eighth goal of the season.
That was one of only three shots on goal in the match, as the hosts did not do enough to force an equaliser and now find themselves five matches without a win, while it was a first win in seven for Sirius.
Follow the rest of Round 19 in the Allsvenskan on Flashscore this weekend.