Gustavo Manduca's last-minute winner meant APOEL Nicosia remained unbeaten at the top of Group G after their Champions League clash against FC Porto.
Ailton Almeida scored the opening goal from the penalty spot against the run of play before Porto striker Hulk equalised in the 89th minute, also from the spot.
It looked like the Portuguese side had salvaged a draw after they had dominated possession, but Manduca's 90th-minute winner sealed the win for the reigning Cypriot champions.
The Nicosia-based club only made their first appearance in the Champions League two seasons ago and look to have made huge strides forward since they finished fourth in a group that contained Chelsea, Atletico Madrid and Porto.
APOEL have now won two and drawn two in this season's European campaign, while reigning Europa League champions Porto are in third after Zenit St Petersburg's 1-0 win over Shakhtar Donetsk.
Porto enjoyed the majority of the possession in the first half but were left to rue their inability to convert any of their chances as APOEL sneaked an unlikely lead just before the break.
Porto striker Hulk proved to be a constant threat, forcing APOEL goalkeeper into the action early on with a strike from the middle of the area.
The Brazilian striker was at the heart of the Porto attack and tried to push forward at every opportunity as both sides looked to control possession early on.
Manduca fired a shot over the bar for the Cyprus side in the ninth minute in a rare chance as APOEL struggled to mount any counter-attacks.
Hulk almost opened the scoring for Porto in the 19th minute after a powerful run down the left but his strong shot was cleared at the near post after he failed to create a decent angle.
APOEL striker Almeida then missed the target with a diving header at the near post which hit the base of the upright.
Hulk and Alvaro Pereira combined well down the left but another chance went begging for Porto when Hulk's route into the area was blocked off by the APOEL defence as the Portuguese side failed to find the decisive final ball.
Urko Pardo then made another save, this time from a low, fizzing shot by Hulk, to keep the scores locked at 0-0.
However, it was the home side who opened the scoring in the 42nd minute when Porto defender Eliaquim Mangala fouled Almeida in the area and conceded a penalty.
Almeida stepped up and struck the ball into the bottom right-hand corner from the spot to give APOEL the lead against the run of play.
After the break, Porto continued to make plenty of chances, with Hulk, Joao Moutinho and Fernando Belluschi all seeing their shots neutralised by the home defence.
Hulk looked to have salvaged a point in the 89th minute when he scored from the spot after Marcelo de Oliveira fouled James Rodriguez in the area, however it was not to be as APOEL hit back two minutes later.
Konstantinos Charalambidis fired in a great cross and found Manduca in the box, whose left-footed strike from close range sealed the win for APOEL.
