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