I critiqued the title elsewhere already so let me say here that the screenshot does show code running in Discord's browser context. They didn't send it to an employee and actually pwn the company, as one might understand from the title, but it doesn't strictly say that and I would count finding XSS as close enough. Saying they've pwned Discord, I think is fair enough
The other three companies mentioned though... yeah, they totally pwned the dependency first and foremost
The fact that SVG files can contain scripts was a bit of a mistake. On one hand, the animations and entire interactive demos and even games in a single SVG are cool. But on the other hand, it opens up a serious can of worms of security vulnerabilities. As a result, SVG files are often banned from various image upload tools, they do not unfurl previews, and so on. If you upload an SVG to discord, it just shows the raw code; and don't even think about sharing an SVG image via Facebook Messenger, Wechat, Google Hangouts, or whatever. In 2025, raster formats remain way more accessible and easily shared than SVGs.
This is very sad because SVGs often have way smaller file size, and obviously look much better at various scales. If only there was a widely used vector format that does not have any script support and can be easily shared.
IIUC, an untrusted inline SVG is bad. An image tag pointing to an SVG is not.
<img src="untrusted.svg"> <!-- this is ok -->
<svg from untrusted src> <!-- this is not ok -->
I feel like this is common knowledge. Just like you don't inject untrusted HTML into your page. Untrusted HTML also has scripts. You either sanitize it. OR you just don't allow it in the first place. SVG is, at this point, effectively more HTML tags.
Yeah, it's still insane to me that the SVG can contain scripts. Wholly unnecessary; the DOM subtree it defines could be manipulated by external scripts just fine.
Anyway, I just set `svg.disabled` in Firefox. Scary world out there.
Update: this breaks quite a few things. It seems legitimate SVGs are used more often for UI icons than random diagrams and such. I suppose I shouldn't be surprised. I'll have to rethink this.
Proxying from the "hot" domain (with user credentials) to a third party service is always going to be an awful idea. Why not just CNAME Mintlify to dev-docs.discord.com or something?
This is also why an `app.` or even better `tenant.` subdomain is always a good idea; it limits the blast radius of mistakes like this.
Nice discovery and writeup. Let alone for a 16 yo!.
I've never heard an XSS vulnerability described as a supply-chain attack before though, usually that one is reserved for package managers malicious scripts or companies putting backdoors in hardware.
This feels so emblematic of our current era. VC funded vibe coded AI documentation startup somehow gets big name customers who don't properly vet the security of the platform, ship a massive vulnerability that could pwn millions of users and the person who reports the vulnerability gets...$5k.
If I recall last week Mintlify wrote a blog post showcasing their impressive(ly complicated) caching architecture. Pretending like they were doing real engineering, when it turns out nobody there seems to know what they're doing, but they've managed to convince some big names to use them.
Man, it's like everything I hate about modern tech. Good job Eva for finding this one. Starting to think that every AI startup or company that is heavily using gen-ai for coding is probably extremely vulnerable to the simplest of attacks. Might be a way to make some extra spending money lol.
Slightly related, as someone who doesn’t engage in this type of work, I’m curious about the potential risks associated with discovering, testing, and searching for security bugs. While it’s undoubtedly positive that this individual ultimately became a responsible person and disclosed the information, what if they hadn’t? Furthermore, on Discord’s side, what if they were unaware of this person and encountered someone attempting to snoop on this information, mistakenly believing them to be up to no good? Has there been cases where the risk involved wasn’t justified by the relatively low $4k reward? Or any specific companies you wouldn’t want to do this with because of a past incident with them?
I run an infosec firm and we have done attacks like this on my clients over and over and over in audits. I always say any bored teen could do most of what we do because most companies are moving too fast feature farming to have any time for responsible security hardening, and now I have yet another great citation.
Unfortunately a competitive rate agreed to in advance with a company before we do any pentesting is the only way we have ever been able to get paid fairly for this sort of work. Finding bugs in the wild as this researcher did often gets wildly underpaid relative to the potential impact of the bug, if they pay or take it seriously at all.
These companies should be ashamed paying out so little for this, and it is only a matter of time before they insult the wrong researcher who decides to pursue paths to maximum profit, or maximum damage, with a vuln like this.
if you click on the link because it has discord.com in the domain the script in the SVG can (maybe) get your session data. Not actually sure if that’s true though, I suppose it depends on how the cookies are scoped
How these companies don't hire kids like Daniel for pennies on the dollar and have him attack their stacks on a loop baffles me. Pay the kid $50k/yr (part time, he still needs to go to school) to constantly probe your crappy stacks. Within a year or two you'll have the most goddamn secure company on the internet - and no public vulns to embarrass you.
I wonder if this analogy could work: if some random visitor pointed out your storage room's key is nearly broken and anybody could come in now and steal your store's stock. You'd be thankful, but would you hire them to come from time to time to check if they have any other insight ? Probably not ?
If you really saw a recurring security risk you'd have many other better use of your money.
Having been adjacent to this for years, it's because it's a cost center and not attached to the bonus of any product or program manager. Every now and then we'll get an advocate for security/integrity at a company but the effort lives and leaves with them.
Microsoft, after getting beat up over this for decades, is still horrible at it. In my area they're have been enforced regulations for years but they're written by the industry itself and infected with compliance managers and thus result in wastes of effort that makes compliance managers that came over from HR and legal happy with their eternal job security and minimal hard work.
Until some heavy handed top down regulation, written by people who understand the nature of ongoing security and software and embedded lifecycles, it's going to stay like this. Most existing supply chain regulation I've seen ends up saying "vet your vendors" and gives minimal practical guidance of how to actually do that. Likelihood of some really good law coming out of the current US administration and business climate is left as a comedy for the reader.
Just because he found one vulnerability at one vendor used by Discord doesn't mean he'll find all the vulnerabilities that exist at Discord or indeed any of them.
It’s clear to me now that I need to set up my home machine the way I set up BYOD when I was contracting last. I need a separate account for all of my development.
I have a friend who at one point had five monitors and 2 computers (actually it might be 3) on his desk and maybe he’s the one doing it right. He keeps his personal stuff and his programming/work stuff completely separate.
Mintlify security is the worse I have even encountered in a modern SaaS company.
They will leak your data, code, assets, etc. They will know they did this. You will tell them, they will acknowledge that they knew it happened, and didn't tell you.
Your docs site will go down, and you will need to page their engineers to tell them its down. This will be a surprise to them.
I've been following the rise of SVG based attacks recently... It's not just hypothetical anymore... People are using SVG files to deliver full phishing pages and drive by downloads by hiding JavaScript in the markup
ALSO as someone who maintains a file upload pipeline I run every SVG through a sanitizer... Tools like DOMPurify remove scripts and enforce a safe subset of the spec... I even go as far as rasterizing user uploaded vectors to PNG when possible
HOWEVER the bigger issue is mental... Most folks treat SVG like a dumb image when browsers treat it like executable content... Until the platform changes that expectation there will always be an attack surface
One of these days I'm gonna have to learn why cross-site scripting even matters, especially with modern browsers restricting a script's access to anything local
The "Hello world" examples always show using it to steal your cookies, which obviously doesn't work now when nearly every site uses the "httpOnly" flag which makes the cookie inaccessible to JavaScript, but really, stealing your session isn't necessary. They just have to make the XSS payload run the necessary JavaScript.
Once the JavaScript is running on the page, all bets are off. They can do ANYTHING that the page can do, because now they can make HTTP requests on your behalf. SOP no longer applies. CSRF no longer protects you. The attacker has full control of your account, and all the requests will appear to come from YOUR browser.
It's a good question and one mature orgs ask themselves all the time. As you can see from most of the replies here, XSS captures the fancy of the bug bounty crowd because there are tonnes of hypothetical impacts so everyone is free to let their imagination run wild when arguing with triagers. It's also the exploit nonpareil for nerdsnipers because sanitisation is always changing and people get to spend their days coming up with increasingly ridiculous payloads to bypass them. In reality, find me one active threat actor who has compromised a business lately with an XSS. It's not an irrelevant risk, but the attention it gets is wildly disproportionate to its real-world impact.
The linked site https://heartbreak.ing/ explains that Mintlify disabled CORS, so that 3rd party sites can run code in your Mintlify-using environment (X, Vercel, etc).
The OP site says that .svg files can only run scripts if they are directly opened, not via <img> tags.
Given this (including the linked writeup on the mintlify RCE), after the React RCE, if think it should be pretty obvious that
1. content security policies should always be used to prevent such scripts (here they would prevent execution of scripts from the SVG)
2. The JavaScript ecosystem should be making ` --disallow-code-generation-from-strings` a default recommendation when running NodeJS on the server.
Vercel (and other nodejs as a service providers) should warn customers that don't use CSP and `--disallow-code-generation-from-strings` that their settings should be improved.
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[ 3.5 ms ] story [ 80.1 ms ] threadThe other three companies mentioned though... yeah, they totally pwned the dependency first and foremost
This is very sad because SVGs often have way smaller file size, and obviously look much better at various scales. If only there was a widely used vector format that does not have any script support and can be easily shared.
Anyway, I just set `svg.disabled` in Firefox. Scary world out there.
This is also why an `app.` or even better `tenant.` subdomain is always a good idea; it limits the blast radius of mistakes like this.
I've never heard an XSS vulnerability described as a supply-chain attack before though, usually that one is reserved for package managers malicious scripts or companies putting backdoors in hardware.
If I recall last week Mintlify wrote a blog post showcasing their impressive(ly complicated) caching architecture. Pretending like they were doing real engineering, when it turns out nobody there seems to know what they're doing, but they've managed to convince some big names to use them.
Man, it's like everything I hate about modern tech. Good job Eva for finding this one. Starting to think that every AI startup or company that is heavily using gen-ai for coding is probably extremely vulnerable to the simplest of attacks. Might be a way to make some extra spending money lol.
Unfortunately a competitive rate agreed to in advance with a company before we do any pentesting is the only way we have ever been able to get paid fairly for this sort of work. Finding bugs in the wild as this researcher did often gets wildly underpaid relative to the potential impact of the bug, if they pay or take it seriously at all.
These companies should be ashamed paying out so little for this, and it is only a matter of time before they insult the wrong researcher who decides to pursue paths to maximum profit, or maximum damage, with a vuln like this.
Ok, you got "https://discord.com/_mintlify/_static/hackerone-a00f3c6c/lma..." to send a controlled payload
But regular users will never hit "https://discord.com/_mintlify/_static/hackerone-a00f3c6c/lma...", so they will never execute your script
I fail to understand how this can be exploited, by whom and in what conditions
If you really saw a recurring security risk you'd have many other better use of your money.
Microsoft, after getting beat up over this for decades, is still horrible at it. In my area they're have been enforced regulations for years but they're written by the industry itself and infected with compliance managers and thus result in wastes of effort that makes compliance managers that came over from HR and legal happy with their eternal job security and minimal hard work.
Until some heavy handed top down regulation, written by people who understand the nature of ongoing security and software and embedded lifecycles, it's going to stay like this. Most existing supply chain regulation I've seen ends up saying "vet your vendors" and gives minimal practical guidance of how to actually do that. Likelihood of some really good law coming out of the current US administration and business climate is left as a comedy for the reader.
But who knows.
Just because he found one vulnerability at one vendor used by Discord doesn't mean he'll find all the vulnerabilities that exist at Discord or indeed any of them.
It wouldn't surprise me if he's in this thread - curious what his thoughts would be.
no, he needs to make his own agency
I have a friend who at one point had five monitors and 2 computers (actually it might be 3) on his desk and maybe he’s the one doing it right. He keeps his personal stuff and his programming/work stuff completely separate.
Mintlify security is the worse I have even encountered in a modern SaaS company.
They will leak your data, code, assets, etc. They will know they did this. You will tell them, they will acknowledge that they knew it happened, and didn't tell you.
Your docs site will go down, and you will need to page their engineers to tell them its down. This will be a surprise to them.
Found by a 16 year old, what a legend.
ALSO as someone who maintains a file upload pipeline I run every SVG through a sanitizer... Tools like DOMPurify remove scripts and enforce a safe subset of the spec... I even go as far as rasterizing user uploaded vectors to PNG when possible
HOWEVER the bigger issue is mental... Most folks treat SVG like a dumb image when browsers treat it like executable content... Until the platform changes that expectation there will always be an attack surface
The "Hello world" examples always show using it to steal your cookies, which obviously doesn't work now when nearly every site uses the "httpOnly" flag which makes the cookie inaccessible to JavaScript, but really, stealing your session isn't necessary. They just have to make the XSS payload run the necessary JavaScript.
Once the JavaScript is running on the page, all bets are off. They can do ANYTHING that the page can do, because now they can make HTTP requests on your behalf. SOP no longer applies. CSRF no longer protects you. The attacker has full control of your account, and all the requests will appear to come from YOUR browser.
The OP site says that .svg files can only run scripts if they are directly opened, not via <img> tags.
So how does the attack work?
I have this feeling with almost all web tools I am required to use nowadays.
No trust.
1. content security policies should always be used to prevent such scripts (here they would prevent execution of scripts from the SVG)
2. The JavaScript ecosystem should be making ` --disallow-code-generation-from-strings` a default recommendation when running NodeJS on the server.
Vercel (and other nodejs as a service providers) should warn customers that don't use CSP and `--disallow-code-generation-from-strings` that their settings should be improved.
There are a bunch of other NodeJS flags that maybe you should look into too: https://sgued.fr/blog/react-rce/#node-js-mitigations