this post was submitted on 10 Jul 2023
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Hi all,

If you're just now signing in for the first time in 12+ hours, you may just now be finding out that Lemmy World and other instances where hijacked. The hijackers had the full abilities of hijacked user, mod, and admin accounts. At this time, I am only aware of instance defacing and URL redirections to have been done by the hijackers.

If you were not forced to sign back in this morning, contact your instance admin to verify mitigations were completed on your instance.

How?

This occurred due to an XSS attack in the recently added custom emojis. Instance admins should follow the issue tracker on the LemmyNet GitHub, as well as the Matrix Chat. Post-Incident Activity is still on-going.

Currently, it is likely that just your session cookie was stolen, with instance admins being targeted specifically by checking for navAdmin, an HTML element only instance admins had. I do not believe this to affect users across instances, but I have yet to confirm this.

What happens next?

As I am not the developers or affected instance admins, I cannot make any guarantees. However, here is what you'll likely see:

  1. Post Incident investigation continues. This will include inspecting code, posts, websites, and more used by the hijackers. An official incident writeup may occur. You should expect the following from that report:
  • Exactly what happened, when.
  • The incident response that occurred from instance admins
  • Information that might have helped resolve the issue sooner
  • Any issues that prevented successful resolution
  • What should have been done differently by admins
  • What should be improved by developers
  • What can be used to identify the next attack
  • What tools are needed to identify that information
  1. A CVE is created. This is an official alert of the issue, and notifies security experts (and enthusiasts), even those not using lemmy, about the issue.

  2. A code security audit is done. This will likely just be casual reviews by technical lemmy users. However, I will be reaching out to the Mozilla Foundation and Cure53 as they recently did an audit of Mastodon. If there is interest in an external audit of lemmy and the costs are affordable, I'll look into crowdfunding this cost.

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[–] [email protected] 198 points 1 year ago* (last edited 1 year ago) (3 children)

This incident made me realize not to use an admin account for my primary lemmy account in my personal instance. I setup another account for instance admin purpose (with 2FA enabled) and keep it logged out, then remove my primary account from the instance admin list.

[–] [email protected] 75 points 1 year ago (3 children)

This is a good mindset in general, when working in AWS you are not supposed to use your root account unless it's absolutely necessary even if you are the only user. Hosting a Lemmy instance should be no different.

[–] [email protected] 9 points 1 year ago

Yeah, even in Windows or what-have-you, you should always keep your admin account separate from your daily driver account for exactly this reason.

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[–] [email protected] 16 points 1 year ago (4 children)

I work with 2 factor, Oath, SAML, etc. all the time for work, and for the life of me I can't get it working properly with Lemmy.

[–] [email protected] 20 points 1 year ago (3 children)

Lemmy decided to go with SHA256 for TOTP seed. This is a very odd move since many 2FA apps don’t support SHA256. I actually had to write a quick python script to spit out my 2FA code since Bitwarden doesn’t support it. Hopefully either Lemmy will change to SHA-1 or Bitwarden will start to support SHA256 seeds.

[–] [email protected] 17 points 1 year ago* (last edited 1 year ago) (8 children)

Wait, I use bitwarden and it works just fine. And yes, it's using SHA256.

Screenshot:

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[–] [email protected] 12 points 1 year ago (1 children)

SHA-1 has been broken already.

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[–] [email protected] 10 points 1 year ago

Preferably the latter, nobody should really be using SHA1 for anything security focused and new

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[–] [email protected] 98 points 1 year ago (1 children)

Having recently migrated from Reddit (and kept up with commercial social media hacks) I'm used to Nothing To See Here! We totally didn't store your personal information in plaintext for hackers to snatch. Oh and maybe please change your passwords. All Part Of The Show!

So, by comparison, the response here is downright heartwarming.

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[–] [email protected] 72 points 1 year ago (5 children)

If there is interest in an external audit of lemmy and the costs are affordable, I’ll look into crowdfunding this cost.

It could get VERY, VERY expensive... depends on code complexity.

[–] [email protected] 70 points 1 year ago* (last edited 1 year ago) (1 children)

Not at this stage.
Lemmy grew too fast, got many more eyes.
Step 1 is getting a security focus group selected from the people who contribute code to lemmy.

Just like the admins and coders volonteer their time, security specialists will too, money might be needed, but that is not in the the first steps.

[–] [email protected] 15 points 1 year ago

Agreed, this is wise.

[–] [email protected] 25 points 1 year ago (3 children)

Yeah, specifically why I mentioned "affordable".

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[–] [email protected] 11 points 1 year ago (1 children)
  1. Set up a fake Nazi lemmy
  2. Have it online during the next Chaos Communication Congress
  3. ???
  4. 50 CVEs.
[–] [email protected] 17 points 1 year ago (1 children)
  1. Be Lemmy Devs
  2. Loudly Claim Lemmy is Bulletproof and unhackable
  3. ???
  4. 50 CVEs
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[–] [email protected] 30 points 1 year ago (1 children)
[–] [email protected] 47 points 1 year ago (3 children)

Only Lemmy instances with custom emoticons were affected based on the Recap of the Lemmy XSS incident. So if Lemmy.ml doesn't have these it should not have been affected.

[–] [email protected] 10 points 1 year ago (2 children)

I think generally the less flashy features (pun intended) the better. Text and links (and well sanitized) is all we need.

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[–] [email protected] 28 points 1 year ago

A code security audit is done. This will likely just be casual reviews by technical lemmy users. However, I will be reaching out to the Mozilla Foundation and Cure53 as they recently did an audit of Mastodon. If there is interest in an external audit of lemmy and the costs are affordable, I’ll look into crowdfunding this cost.

You don't need to pay money. You just need to listen to the recommendations already made by free tools.

Here, fix this shit first and then worry about a professional audit later.

[–] [email protected] 24 points 1 year ago (6 children)

also, I cannot properly login into my lemmy.world account anymore. username/password work, but when I try to upvote it tells me i gotta be logged in. Tried apps and web.

[–] [email protected] 14 points 1 year ago (3 children)
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[–] [email protected] 10 points 1 year ago

Try clearing cookies (or app cache, on app), that will most likely resolve the issue.

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[–] [email protected] 24 points 1 year ago (5 children)

How do I contact my instance admin?

I went ahead and logged out and back in on my own, but I was not prompted to do so by Lemmy and I don't know enough about this stuff to say whether or not doing it on my own would've helped. I'm still pretty overwhelmed trying to figure this site out, so I apologize if this is a dumb question, just want to make sure I'm doing what I can to protect my own privacy.

I don't want to fall for the millennial version of a Nigerian prince scam, lol.

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[–] [email protected] 23 points 1 year ago (2 children)

Good reminder that: small instances = small impact. Both true for the positive and the negative.

[–] [email protected] 16 points 1 year ago (1 children)

Or if you're on a small instance, you're a lot less likely to be targeted in the first place.

[–] [email protected] 15 points 1 year ago (1 children)

Security by obscurity is the best policy I always say 😉

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[–] [email protected] 10 points 1 year ago

Not sure that’s entirely true. Thankfully this attack vector required custom emojis, so it was limited to those specific Lemmy instances. Other attack vectors we may not be so lucky and it could spread through federation.

[–] [email protected] 18 points 1 year ago (1 children)

Good thing we don't have custom emojis on monero.town and the admin account isn't used for things outside of the local community :D

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[–] [email protected] 17 points 1 year ago (2 children)

XSS, classic

Thanks for your hard work, fuck the trolls that always have to poke holes in shit

[–] [email protected] 38 points 1 year ago (4 children)

Honestly, I see it as a win.

The people that did this didn't really act out in a coordinated attack. They were just kind of playing around, redirecting to lemonparty, changing page elements.

It could have been a lot worse. The site could have been redirecting to malicious websites, downloading trojans, doing a lot of bad things. Instead, we got direct attention to the security vulnerabilities in question, and they're being worked on and patched out relatively quickly. Helps that a lot of those on these communities are focused in programming and cybersecurity.

[–] [email protected] 14 points 1 year ago (1 children)

The fundamental issue is not that emoji XSS (that's just a vector), but how JWTs are implemented and [not] secured. I've read that it was reported at least this January (https://akkoma.nrd.li/notice/AXXhAVF7N5ZH1V972W).

So, developers were already aware, yet - as I'm checking 0.18.1 - they have not fixed the unsafe-inline and unsafe-eval CSP, haven't made jwt cookie HttpOnly, and haven't done anything about exp and jti in the JWTs. I hope the recent events will make them do to so, and not just patch this particular XSS.

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[–] [email protected] 10 points 1 year ago

That's fair, I was a little harsh. Not all hackers are looking to cause damage!

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[–] choroalp 16 points 1 year ago (2 children)
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[–] [email protected] 12 points 1 year ago (1 children)

This post is weird. You're typing like you're in charge of things, but you're apparently not.

It's one thing to show some initiative, but you're literally demanding a full report like the Lemmy devs work for you. You sound like someone who does this kind of thing for a living and felt the need to flex. Because otherwise, what the hell are you even doing?

Setting neurotically-specific demands for the developers makes sense if you represent a big instance or something, but you're literally just a dude. You could have framed this entire post in a different way and gotten away with it. Right now, it's creepy to anybody who actually reads the entire thing.

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