Malmö supporters were not satisfied with their team's performance, and threw several pyrotechnic devices at Strandvallen after Villiam Granath's 4–0 goal in the 63rd minute.
The match was paused for a little over fifteen minutes before play could resume.
Elliot Stroud opened the scoring in the 17th minute, and Jacob Bergström made it 2–0 ten minutes later.
MFF's 17-year-old Theodor Lundbergh headed home to make it 3–0 after the hour mark, and the home team's Granath made it 4–0 four minutes later.
Young Lundbergh drew his second yellow card in the final minutes and, in addition to his earlier goal, was also sent off.
Mjällby will face Gais in the semi-finals, who won their quarter-final against AIK earlier on Saturday. That match will be played next Saturday.
