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Lemmy.world (and some others) were hacked (lemmy.world)

submitted 1 year ago* (last edited 1 year ago) by ruud@lemmy.world to c/lemmyworld@lemmy.world

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While I was asleep, apparently the site was hacked. Luckily, (big) part of the lemmy.world team is in US, and some early birds in EU also helped mitigate this.

As I am told, this was the issue:

There is an vulnerability which was exploited
Several people had their JWT cookies leaked, including at least one admin
Attackers started changing site settings and posting fake announcements etc

Our mitigations:

We removed the vulnerability
Deleted all comments and private messages that contained the exploit
Rotated JWT secret which invalidated all existing cookies

The vulnerability will be fixed by the Lemmy devs.

Details of the vulnerability are here

Many thanks for all that helped, and sorry for any inconvenience caused!

Update While we believe the admins accounts were what they were after, it could be that other users accounts were compromised. Your cookie could have been 'stolen' and the hacker could have had access to your account, creating posts and comments under your name, and accessing/changing your settings (which shows your e-mail).

For this, you would have had to be using lemmy.world at that time, and load a page that had the vulnerability in it.

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[-] AlmightySnoo@lemmy.world 32 points 1 year ago* (last edited 1 year ago)

Do we have any details on how Michelle's account was compromised? Right now in the GitHub issue about the vulnerability they're clueless about how the custom emoji exploit could be performed without first an already compromised admin account.

EDIT: yeah here's how: https://github.com/LemmyNet/lemmy-ui/issues/1895#issuecomment-1629326627

You do NOT need an admin account to do that. Any normal user could have done that.

[-] Caoldence222@lemmy.world 9 points 1 year ago

They are incorrect I believe. An unprivileged account could change the markdown to contain malicious code before posting. Though through the admin panel one could modify an emoji and make the code embed anywhere that emoji was used not just where the attacker posted it.

Source: I watched it happen on hexbear.net (there they did not get any admins, but there was an attempt)

[-] AlmightySnoo@lemmy.world 5 points 1 year ago* (last edited 1 year ago)

An unprivileged account could change the markdown to contain malicious code before posting.

How? I kept trying it yesterday without any luck, even with manual POST requests. The markdown (at least in the comments) seems to be properly escaped.

[-] Caoldence222@lemmy.world 6 points 1 year ago

you'd have to find an unpatched instance to try it on I guess, I'm just telling you what I saw. Maybe hexbear's emoji code was modified from upstream. What happened there was:

A new user showed up and posted one emoji in the megathread to get a couple of established accounts' tokens, and then used those established accounts to first, DM spam the admins with the token stealer, then when that failed, spam porn/gore. It was cleaned up in nearly real time, and they definitely didn't compromise an admin account first.

I can look for more details in a bit

[-] AlmightySnoo@lemmy.world 7 points 1 year ago* (last edited 1 year ago)

I just figured out how: https://github.com/LemmyNet/lemmy-ui/issues/1895#issuecomment-1629326627

Yeah, an admin account is absolutely not necessary.

[-] tarjeezy@lemmy.ca 7 points 1 year ago

So, simply viewing a comment thread with a maliciously-altered emoji (on an unpatched instance) was enough to compromise your account?

[-] MichelleG@lemmy.world 20 points 1 year ago

Pretty much. The hacker sent me a DM with the emoji which contained the malicious code. All I did was open and read it. I’m proud of the team that worked until 2 AM to not only revert the changes, but fix the exploit.