Incoming essay alert! Lol.
TL;DR: Think it's Quinn / someone Quinn-adjacent, but could be Derek or another Alpha.
Could be someone we haven't even met yet or is currently an extremely minor character. We're still getting introduced to new characters all of the time. What's weird is that the MC is getting blamed for it. I think it's just because he's an easy target and had very visible confrontations with Chad (as opposed to being specifically targeted). So far this has been supported by the story, but could easily change with further context. We also know next to nothing about Chad's backstory except that:
1) He's gay, and
2) He's the (now former) leader of the Alphas.
Maybe he's related to someone important that's been causing a big headache for Burke / the school. Maybe someone noticed him bullying MC and wanted to teach him a lesson. Maybe he's a nobody but just the head jock, and someone wants to butt him out and take his place.
Maybe it's not about Chad at all, but is about Sage instead.
- It could be someone like Caleb trying to butt Chad out and take his place as the new head of the Alphas. We don't know much about the other Alphas right now, but the current appearance is that they're all on Chad's side. That could change if any of them have an anti-LGBT stance. The enduring stereotype has been that Jocks "can't" be gay, but I expect DPC to take this trope and turn it on its head as far as the Alphas are concerned.
- Could be someone like Quinn, who keeps things close to her chest and manipulates and manipulates and manipulates. Quinn has a lot to gain if Sage is distracted with Chad's infidelity, and Chad being blackmailed makes him fearful of not being able to come out on his own terms. Also, Riona, who Quinn keeps under a very tight leash. (Highly, highly doubt it's Riona acting on her own.)
- Could be Derek. Really, really hope it's not Derek. There's a scene with Burke viewing the video about the MC/Jade if MC tells Derek about it, which is likely a red herring to make us suspicious of Derek early on. Granted, that leads to the Jade video being uploaded into the DIK laptop, so... could easily be a different DIK responsible (or someone like Quinn to remove an obstacle like Rusty since he seems like a good dude).
- However -- Derek has access to the drone before the end of Ep 3. We never actually see the pictures, let alone the angles of the pictures, so could just as easily be a drone picture. The first time we meet Derek is directly after the MC's first confrontation with Chad, so he's very aware of the friction between the two. Additionally, Derek is aware of the friction between MC and his former roommate Troy. They were in the same dorm -- wouldn't be out of the question for Derek to see Chad sneaking into Troy's room and putting two and two together.
Without further context, it's hard to make real guesses right now.
- If it's someone like Derek, why? To goad Chad into giving MC a temporary beating that he'll recover from, but (hopefully) resulting in a permanent expulsion of MC's aggressor? Decent motive, one I could see Derek possibly doing under the guise of "I did it for you bro", but really hoping it's not him given his knowledge and support of Maya and her sexuality. There are people who think that female-female relationships are fine, but male-male relationships are not, so I'm hoping DPC doesn't write Derek to be one of them. I think it would weaken his character arc.
- If it's Quinn, why? To distract Sage from focusing on her HOT duties, allowing Quinn to get away with anything and everything she's doing behind Sage's back, and solidify her hold over the new HOTS? This, to me, is the strongest motive so far.
- If it's Caleb or another Alpha, why? To be the new leader? Story-wise not a great motive, but not everything has to be a giant conspiracy. Some people are just inherently selfish and want to step on other people for their own self-interest.
I wrote all of that just to say -- Despite being a little suspicious, given the information we currently have I don't think it's going to be Derek unless DPC reveals something crazy in EP8.
I think it IS going to be Quinn, or someone Quinn-adjacent. Even if she didn't directly dirty her hands with it, Quinn gains the most with Sage being distracted from her HOT duties as President. She likely ordered someone like Riona to take the pictures. Cracks are beginning to form there as of EP 7, but in EP 3 Riona was fully under Quinn's thumb. If you're in the process of beginning a sexual relationship with her, Quinn might even tell the MC about it if she's put under enough pressure or if she gets beat up again. Or, if she's bragging and is high enough, maybe she'll spill the beans to the MC in that way. If Riona is feeling paranoid enough, she might open up to MC if she was responsible for the pictures.
I expect we're going to finally get some back story on Chad next episode and finally resolve the blackmailing mystery. If not in the episode itself, then definitely in the final moments leading to the season cliffhanger.
EDITED TO ADD:
I saw someone write that they think it could possibly be Troy to get Chad to force Chad to come out and be open about their relationship. Also a potentially viable option, but possibly harder for Troy to coordinate (unless Melissa is Troy's sister (as some have predicted)). Melissa could have made a plan with Troy to out Chad so that Chad will finally be out in the open with him. We'll see what happens!
