Bayer Leverkusen won 3-2 at FC Copenhagen and a late goal gave Steaua Bucharest a 1-0 home win over Ludogorets Razgrad in the other first leg ties.
Austrian champions Salzburg, who have been eliminated in the qualifiers six times since Red Bull's takeover in 2005, once again made life difficult for themselves against Malmo.
Franz Schiemer and Soriano put them 2-0 up in less than an hour and the Spaniard also hit the woodwork three times as Salzburg dominated the game.
But the game ended farcically for the hosts when a mix-up between Schiemer and keeper Peter Gulacsi in the 90th left Emil Forsberg to tap into an empty net for the 1979 European Cup runners-up, who have never played in the group stage.
Denmark's chances of having two sides in the group stage for the first time look remote after Copenhagen's home defeat against seasoned campaigners Leverkusen.
Stefan Kiessling gave the Bundesliga side a fifth minute lead, only for the Danes to hit back with headed goals by Mathias Joergensen and Daniel Amartey before 15 minutes was up.
Karim Bellarabi and Son Heung-Min replied before half-time for Leverkusen who should wrap up the tie at home on August 27.
Former European champions Steaua Bucharest gave themselves a slender lead to take to Bulgaria when Alexandru Chipciu scored the only goal in the 88th minute.
- Sports & Recreation
- Bayer Leverkusen
- Gonzalo Higuain
- Franz Schiemer