The React2Shell Story (opens in new tab)

R2S was a painful one, but Lachlan was a dream of a security researcher to partner with. Not just from a responsible disclosure POV, but things like hopping on multiple calls with Meta and our team to help us validate remediations. Thank you Lachlan for helping make the internet safer (and great job on figuring out this 'labyrinth' of a vulnerability)

A great read. Sylvie's writeup is good too: https://sylvie.fyi/posts/react2shell/

I'm still yet to be convinced React Server Components are anything but a disaster to the developer experience. Mixing backend and frontend without a clear boundary is terrible for any codebase beyond a handful of contributors.

I wish this site respected prefers-reduced-motion. The dots on the background give me motion sickness while trying to read. Thank goodness for Firefox reader mode.

Nice read!

I love the "we are so back" vs. "it's so over" graph. Defines so much of this type of work. "Wow? ... nah... WOW?! ... nah..."

>> Amazingly, despite being a weekend, the Meta team triaged, reproduced, and confirmed my submission in around 17 hours.

Incredible. Realize what you have done from start to finish (with confirmation) in < 24 hours.

I was really surprised when this hit, and I discovered the protocol was essentially undocumented / unspecified. I was trying to find indicators of compromise and that was made more difficult by the lack of documentation.

It was really helpful that they had coordinated with WAF providers like cloud flare ahead of disclosure to put rules in place though.

Haha, nice.

One correction: The link in "To be honest, I'm not even sure if I understand it, but it's on my GitHub." goes to the wrong file (01 instead of 00).

Boy I loved this write up, and really loved Sylvie’s, which gives a peek into the economic side of this white hat hacking — prepping, safety, wondering who you trust, preparing to claim as many bug bounties as possible.

I was struck by the very sensible economic filter: “who is vulnerable that has a bug bounty program?” Incredibly good reminder that you should have a bug bounty program; otherwise, nobody might call you. Until, you know, you’ve been compromised.

What a great write-up. Thanks for sharing how you found this fascinating vulnerability and exploit.

The first exploit looks somewhat like an elaborate json version of the bf language.

Side note: A few weeks ago I started to see floaters in my eyes and the background for your site is making my brain go haywire. Also a tad bit distracting while trying to read the article.

Really cool article btw.

Really nice writeup. Would be intresting If an ai can find such vulns, too.

> But that afternoon, fueled by curiosity and frustration, I felt a switch flip in my brain, and I dived head-first into a rabbit hole with no turning back.

https://xkcd.com/356/

It happens to all of us. However, I think it’s much easier nowadays with LLMs for something productive like this to come out of it. I can notice something wrong and triage or even fix it before the point where I’d normally start to feel the subconscious pull of opportunity cost telling me to stop.

Whoda thunkit that

- blurring the lines between client code and server code

- creating a brand new protocol for communication between trusted and untrusted actors

- and with all of that allow the protocol to serialize code and not just primitives

Would be a tremendously stupid idea. And for what? To lock developers further into the react ecosystem. What a shitshow react continues to be.