Victory & Curse Timing Clarification

In a game recently, a player had a curse that read something like this:

After the cursed Cult advances on their summon track, retreat their summon track one space.

(This is not the exact wording, but a paraphrasing, as I do not have the cards in front of me.)

So, eventually, the player with that curse advanced her summon track to the victory space, but that also triggered the curse.

So, my question is: Which is triggered first? The fulfillment of the victory condition, thus letting that player win? Or the curse, thus preventing the player from winning?