In this case “sex” would typically be considered to still be a noun; it’s just taking a more adjective-like role in the phrase. In English, and especially in headlinese, it’s common to place two nouns together like this, with the first modifying the second. The noun “sex” is called an https://en.wikipedia.org/wiki/Noun_adjunct in this context, and “orgy” is its head noun.
This particular phrase actually contains 5 of these attributive-head relationships. I can’t be sure, since it’s nigh-impossible to parse the headline, but I think that “Ferrari” is an attributive whose head is “sex”. If we were to say that “sex” is an adjective just because it’s modifying the noun “orgy”, we’d also be forced to conclude that “Ferrari” is an adverb because it’s modifying an adjective.