These wiz.io blog posts should be banned from HN; AFAICT, they're AI generated. Here's the original post with the details: https://react.dev/blog/2025/12/03/critical-security-vulnerab... - the vulnerability was not found by a Wiz employee at all, and the Wiz article (unlike the react.dev article) does not provide any meaningful technical information.
The important part to know:
- Even if your app does not implement any React Server Function endpoints it may still be vulnerable if your app supports React Server Components.
- The vulnerability is present in versions 19.0, 19.1.0, 19.1.1, and 19.2.0 of: react-server-dom-webpack, react-server-dom-parcel, react-server-dom-turbopack
- Some React frameworks and bundlers depended on, had peer dependencies for, or included the vulnerable React packages. The following React frameworks & bundlers are affected: next, react-router, waku, @parcel/rsc, @vitejs/plugin-rsc, and rwsdk.
What is the "tell"? I'm not saying they are or aren't, but... people say this about literally everything now and it's typically some flimsy reasoning like "they used a bullet point". I don't see anything in particular that makes me think ai over a standard template some junior fills out.
>the vulnerability was not found by a Wiz employee at all
I've re-read the Wiz article a few times. Maybe I'm just dumb, but where did Wiz claim to have found this vulnerability?
Hackernews' submission guidelines clearly state: "Please submit the original source. If a post reports on something found on another site, submit the latter." [0]
The Wiz post has significantly changed since it was first published (and how it looked when first posted to HN), FYI -- see [1]. When it was published, it was a summary of the React announcement, and was somehow longer than the original and yet provided less useful information than the original.
In any case, the "tell" is the syntactic structure (as Chomsky would say) and certain phrases used in the post.
>in case you aren't aware as to where to find them
The guidelines are linked at the bottom of every page, and directly underneath the comment box on new accounts. I also, perhaps surprisingly, know how to google "hn guidelines". Or ask chatgpt. Or reply "where's that piece of information from?".
>I think that's a doubly reasonable thing to do, given that your account is new, too.
People link the guidelines and, like, wikipedia to accounts that are 10 years old with 30,000 karma. It's a weird quirk of HN.
If you're talking to someone in real life, or professional emails, or whatever and you provide citations for commonly known things/definitions/etc.... you're being condescending.
> If you're talking to someone in real life, or professional emails, or whatever and you provide citations for commonly known things/definitions/etc.... you're being condescending.
If you're commenting on a public forum and you provide citations for commonly known things/definitions/etc., you're supplying the source of your claims for people who may be unaware. You are not the only reader of their comment (nor this one), even if it is in direct reply to yours.
You're missing the point. You shouldn't take it personally.
> Assuming everyone is an idiot who a) doesn't know something common and b) isn't able to figure out how to google it and c) isn't able to figure out how to say "where's that from?" in a reply
They are implied when someone feels like they need to cite commonly known, easily found, and easily asked about stuff. That’s like the whole reason why it’s condescending
I'm aware that this is your perspective but you should be aware that it is your subjective opinion. Their intention does not appear to be condescending. They did not assume or imply any of those things. Your anger is misplaced with that individual; they didn't hurt you.
Dear jfindper,
I hope this professional email finds you well.
Would you mind reading about HN's approach to comments and site guidelines?
https://news.ycombinator.com/newswelcome.html
Please don't fulminate. Please don't sneer, including at the rest of the community.
Kind regards,
A. Webshitter
When I saw "WIZ Research - Critical Vulnerabilities in React and Next.js" on the big image banner, I immediately thought that Wiz found the vulnerability.
When Reuters has an article that says "Reuters Business - Interest rates going up", do you think Reuters made the interest rates go up themselves or that they are reporting on the interest rates?
Reuters isn’t a bank. Wiz is a security company so they have a greater responsibility to distinguish between their own original work and discoveries made by other researchers.
presentation and formatting aside the constant attempts to manufacture legitimacy and signal urgency are a classic tell. everything is "near-100%" reliable, urgent, critical, reproducible, catastrophic. siren emoji
>Because author says it, it doesn't mean that it is true.
And because random HNer says it is ai doesn't mean it is ai.
>But still, is it so important?
Not to me, no. If the information is useful/entertaining/etc., I don't really care. But having to read "it's ai!" comments on literally every article/blog posted for the next 10 years is going to be super annoying. Especially if the reasoning provided is "they used the word critical". At least you pointed to something kind of interesting with the quotation marks (although, certainly not definitive of anything), rather than saying some extremely common word = ai.
So smart quotes is now an LLM tell? You know that a lot of people write in word processors that automatically replace standard quotes with smart quotes (like, say, MS Word), and that these word processors can then export HTML straight into your block or preserve the smart quotes across a copy & paste? Several blog WYSIWYG editors will also directly insert them as well.
The document doesn't have both in it. It's possible it was edited, but someone else in the thread posted the archive.org original version, and it also doesn't have smart quotes:
(Note also that you can end up with mismatched quotes if you paste in a segment of text from some other source that uses them, which is pretty common in journalism for a fast-changing story.)
>Same way if you read an article full of typos you lose trust in it
Not for long! This seems like this will soon be the only way to put something on the internet without people rabidly saying its ai (at least for a few weeks, until people start prompting for typos to be included).
Hey mmsc, first of all - the blogs are not AI Generated!
Second of all, the blog did add more information
"In our experimentation, exploitation of this vulnerability had high fidelity, with a near 100% success rate and can be leveraged to a full remote code execution. The attack vector is unauthenticated and remote, requiring only a specially crafted HTTP request to the target server. It affects the default configuration of popular frameworks.
"
In the end - if it helped spreading the news about this risk so teams can fix them faster, then this is our end-goal with these blog posts : )
Hey, researcher from Wiz here - we definitely didn't discover these vulns and all the credit goes to Lachlan Davidson. We have been investigating these vulns throughout the day and decided not to disclose the full extent of our conclusions or release a working exploit until more people get a chance to patch this (and as I mentioned in another comment, exploitation works out-of-the-box so you definitely should patch ASAP).
It seems like this vulnerability is yet another prototype pollution vulnerability.
There was a TC39 proposal a few years ago [0] that proposed to block the getting/setting of object prototypes using the bracket notation, which would have prevented this vulnerability.
At the moment, every single get/set with a square bracket, which uses untrusted data, needs to do some manual check to see whether variables contain "bad" keys like `__proto__`, `prototype,` `constructor`, and so on. This is incredibly annoying, and doesn't really fix the issue. It's possible also to freeze an object's prototype, but that causes other issues. It's also possible to use Object.create(null), and Object.hasOwn (also known as Object.prototype.hasOwnProperty), but again, this does not scale because it has to be done _every single time_.
Maybe it's time to revisit this from a language perspective, instead of continuous bandaid fixes for this language-specific vulnerability (a similar language-specific vulnerability exists in Python called class pollution, but it's .. extremely uncommon).
That being said, it _will_ happen if you use your own merge() function like the TC-39 proposal demonstrates, but its because you are using the [] syntax to implement it which can affect __proto__
Side note, JSON.parse() also doesn't let you set the actual prototype:
On Node.js there are some hardening flags like --disable-proto=throw and --frozen-intrinsics to mitigate/crash on prototype pollution, and to prevent dynamic evals with --disallow-code-generation-from-strings - however, Vercel doesn't seem to support custom node runtime options.
Just to simplify this - our exploitation tests so far have shown that a standard Next.js application created via create-next-app and built for production is vulnerable to CVE-2025-66478 without any specific code modifications by the developer - so this is essentially exploitable out-of-the-box.
It looks like it only affects dynamic reloading? If I understand correctly, the client can just politely ask the server to load arbitrary code, and the server agrees.
This should never be enabled in production in the first place. I'm not surprised that they are fundamentally vulnerable, and this is likely not going to be the last RCE in this part of the code.
It's generated code ("compiled" Javascript); I found it easier to read than the "main" diff in React which was (intentionally, I think?) obfuscated with additional changesets.
Unsafe deserialization is a very 2010 Ruby on Rails sort of vulnerability. It is strangely interesting that such a vulnerability was introduced so late in the lifetime of these frameworks. It must be a very sneaky vulnerability given how cautious we have become around deserialization since then.
The React Server Components wire format (Flight) is relatively novel and very new (it has existed in React stable for just a year). This is not a simple JSON parsing bug.
The rails bugs weren't about Json parsing, they were deserializing into Ruby objects of classes that had side effects, and those side effects led to RCE possibilities. Since those happened, you'll find any deserialization library, especially in dynamic languages, will have a safe (or conversely unsafe) deserialize function to make it more explicit that there's risks involved.
It seems like this might be one of the biggest vulnerabilities in recent times...
The default react / nextjs configurations being vulnerable to RCE is pretty insane. I think platform level protections from Vercel / Cloudflare are very much showing their utility now!
It's not entirely JavaScript but it is partially due to some of the language's history and culture: prototype pollution wouldn't be possible in every other language and not everyone has culture around things like decoding payloads in an exploitable manner (e.g. in the Python world some people used to decode pickled objects but it was always frowned upon; the Java world has had debates over the years about this). The big one which is unique to JavaScript is the culture around client-side execution and mixing code running between the two environments, which means you have a lot of machinery setup to execute code on the server and/or clients, making it both easy to have confusion around the execution context in ways which have been exploited and encouraging people to do things like ship complex objects between the two which programmers using other backend languages wouldn't consider because they never had the possibility of running directly in the browser.
Given that most Next.js and RSC apps run on Vercel, I’m wondering if they’re doing the same thing. There’s no information about this in their latest blog post [0].
"Assigned CVE-2025-55182 (React) and CVE-2025-66478 (Next.js), this flaw allows for unauthenticated remote code execution (RCE) on the server due to insecure deserialization."
I don't have time to look into it right now (def later)!
However, I was curious to see if github copilot can reverse engineer it based on the latest commits and seems that what it is saying aligns with both advisories. It pointed out that it has to do with circular reference handling which sounds to me something that can be easily overlooked.
While this analysis might be completely off, the simple fact that I could get even this information without much efforts is mind-boggling. With better setup it might be able to get more.
With AI now being common place, coordinated timely disclosure is even more important considering the stakes. It is theoretically possible to get an exploit working within minutes. Considering that we see one of these major vulnerabilities annually (and it seems to me around the same time of the year) a bad actor can easily capitalise on the opportunities when presented.
> While this analysis might be completely off, the simple fact that I could get even this information without much efforts is mind-boggling. With better setup it might be able to get more.
This can essentially be rephrased as "I don't know if what the LLM said is true or not but the fact it may or may not be correct is amazing!"
Checked. The answer is no (Claude Opus 4.5 with OpenCode). It wasn't even able to write a scanner to check for the vulnerability that worked. I gave it the diffs and various writeups, and the free access to the source and compiled index.js. It kept trying to cheat by editing the source to add a vulnerability and saying that it got an RCE
I tend to agree. Cloudflare and Vercel were able to mitigate in the form of WAF rules, but it's not immediately clear what a user or vendor can do to implement mitigations themselves other than updating their dependencies (quickly!).
IMO the CVE announcement could have been better handled. This was a level 10. If other mitigations can are viable and you know about them, you have a responsibility to disclose them in order to best protect the safety of the billions of users of React applications.
I wonder how many applications are still vulnerable.
The important part to know:
- Even if your app does not implement any React Server Function endpoints it may still be vulnerable if your app supports React Server Components.
- The vulnerability is present in versions 19.0, 19.1.0, 19.1.1, and 19.2.0 of: react-server-dom-webpack, react-server-dom-parcel, react-server-dom-turbopack
- Some React frameworks and bundlers depended on, had peer dependencies for, or included the vulnerable React packages. The following React frameworks & bundlers are affected: next, react-router, waku, @parcel/rsc, @vitejs/plugin-rsc, and rwsdk.