Interesting you touched on his age. I got extremely curious, why did the OP did such a flex?(assumming they are telling the truth). The first sentence is such a weird brag that it felt suspicious. The report is highly technical and extremely well written. We're either dealing with a pure genious or a fraud. But why would a genious flex? Doesn't make sense.
I can believe a very talented 15yo pulling this off. But the number of anonymous "I'm 15 and this is my impressive feat" posts on HN made me wonder if it's just a joke.
The flex is probably because they are 15 and a bit immature.
An anecdote - I used to be the lead for an infotainment security program for a well known manufacturer. They would send me to a lot of small security meetups and training. One in specific was a security training event for some HS students, which I would define as gifted. There were roughly 40 of them, from 14 to 17 years old, and they were all extremely impressive in things ranging from reverse engineering applications to assembly code all the way Linux systems stuff.
Something like this would have been easy for them - I mean the basics of this is that the attacker sends a message to a discord/signal user and then sends a request to a Cloudfare server. Not exactly splitting atoms IMO. What I think is special about this 15 year old in question is the epiphany that it might be possible and then giving it a go. This is the true hacker spirit.
I don't know what you think is genius about any of this, but you're right, the flex is odd. It's something I've been seeing more and more of lately, and I find it off-putting, because, Back In My Day, I never had such a phase, where I felt like I should be given more credit for my 1337 h4xx0r skillz, because I was in high school or whatever—and I don't remember anyone else doing it, either.
I can only assume this is a consequence of modern social media having shifted the Internet from being a bunch of pseudonymous people making and sharing stuff, to everything being myopically focused on one's identity first, and what they do second (as is literally the case here).
And it looks like it works to achieve its desired effect, too—a significant portion of the comments here are congratulating the guy for doing such a thorough technical write-up, given his age. Maybe this is just me being a grumpy “old” man now, but I would've found that condescending when I was his age, and would've rather concealed my age than be condescended to as such. But, to each his own, I suppose.