Lemmy.world (and some others) were hacked

Ruud@lemmy.worldmod to Lemmy.World Announcements@lemmy.world – 2319 points –

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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So thats why MalwareBytes gave me this message yesterday.

Wow that's cool. How did malwarebytes know the website was compromised ?

I think it sees that the browser is trying to execute code that is suspicious (the payload of the XSS was pretty obvious).

I wish I knew. I tried logging into Lemmy yesterday and I was kept giving this message. I thought it might be relevant and saved this snip. I am only about to post this pic now. I did whitelist Lemmy on Malwarebytes after as well.

Interestingly, here is a log when browsing Lemmy over the last week or so.

Believe the derp.foo and .today are both federated instances. Don't know what the other rows are.