My main theory about the published nude photo of Сathy in roster is that Quinn is behind it. This is 99% proven.
The location of Riona next to the library, where Rusty eventually found a laptop, Sarah's monologue and Mel on the couch who seemed to be trying to deflect suspicion from themselves, Camila who distracted Rusty with sex and Quinn who distracted Tommy with conversations. It feels like she brought Josie and Maya on purpose, knowing that Tommy wouldn't like it, and when he ran away, she started talking to him.
The main problem of the theory is motives. The simplest explanation is that Quinn wanted Tommy to become president and organized it, but it's unclear how she could guarantee that the fraternity would not be closed and that funding for weed would continue after Rusty left the presidency.
The second potential customer is the Dаw. We know that at the end of the 3rd episode he came to Quinn himself, and an episode earlier he found out that the Diks fucked her girlfriend Arieth and contributed to the expulsion of Chad from the brotherhood. Moreover, it is Daw we see with photos of Cathy in class and Daw does not get along with Cathy. The important point is that Daw has to offer something so valuable that Quinn has to agree to it. It can be a quid pro quo. Quinn sets up the Diks, and then the jocks destroy the mansion.
The second controversial point is what result the attacker initially sought by publishing an erotic photo. Closing the fraternity?
Take them out of the game for a while? Fire Сathy?
I would not want the disclosure of the strangest things to be the same as with the story of exposing the orientation of Chad. Sage logically noticed that in the video he asked a certain girl to put on panties, to which MS replies that she does not know. This was an important counterargument against the orientation of the Child to which no answer was given.