Here are the Europa League semi-finalists
The Premier League outfit went into their second instalment in Moscow with a comfortable 4-1 advantage, but knew following the comebacks from Roma and Juventus in the Champions League earlier in the week that nothing could be taken for granted.
It turned out to be true as CSKA fought back to bring the tie to 4-3 on aggregrate before two goals from Arsenal at the end of the second half saw off the Russian's charge.
In Portugal, Atletico Madrid were another team seemingly in control of their tie after winning the fixture at the Wanda Metropolitano 2-0.
However, Sporting clawed one goal back through Fredy Montero and looked to be dominating proceedings, pushing for that crucial equaliser, but Atletico held strong to secure their place in the semi-final.
As for Marseille, their tie was finely balanced after losing out in the first leg 1-0 to RB Leipzig.
The game would turn out to be the most action-packed of the night through as the two sides traded blows until the Ligue 1 outfit broke down Leipzig's resistance to win 5-2 on the night and go through 5-3 on aggregate.
The final match-up also produced a hatful of goals and also the biggest comeback of the night. Trailing 4-2 on aggregate going into the return leg, Salzburg stunned Lazio with four goals to win 6-5 overall after the visitors pulled one back through Ciro Immobile.
Salzburg, Marseille, Arsenal and Atletico will now have to wait until Friday afternoon to find out who they will face in the semi-finals.