This post is intended as a central place that admins can reference regarding the
XSS incident from this morning. ### What happened? A couple of the bigger Lemmy
instances had several user accounts compromised through stolen authentication
cookies. Some of these cookies belonged to admins, these admin cookies were used
to deface instances. Only users that opened pages with malicious content during
the incident were vulnerable. The malicious content was possible due to a bug
with rendering custom emojis. Stolen cookies gave attackers access to all
private messages and e-mail addresses of affected users. ### Am I vulnerable? If
your instance has ANY custom emojis, you are vulnerable. Note that it appears
only local custom emojis are affected, so federated content with custom emojis
from other instances should be safe. ### I had custom emojis on my instance,
what should I do? This should be enough to mitigate now: 1. Remove custom emoji
DELETE FROM custom_emoji_keyword; DELETE FROM custom_emoji; 2. Rotate your JWT
secret (invalidates all current login sessions) -- back up your secret first,
just in case SELECT * FROM secret; -- generate a new secret UPDATE secret SET
jwt_secret = gen_random_uuid(); 3. Restart Lemmy server If you need help with
any of this, you can reach out to me on Matrix (@sunaurus:matrix.org) or on
Discord (@sunaurus) ### Legal If your instance was affected, you may have some
legal obligations. Please check this comment for more info:
https://lemmy.world/comment/1064402 [https://lemmy.world/comment/1064402] #####
More context: https://github.com/LemmyNet/lemmy-ui/issues/1895
[https://github.com/LemmyNet/lemmy-ui/issues/1895]
https://github.com/LemmyNet/lemmy-ui/pull/1897
[https://github.com/LemmyNet/lemmy-ui/pull/1897]
You can read the breakdown of the XSS incident at Lemmy.world.
This won’t be an issue for Wayfarers’ Haven because we don’t actually have any custom emoji.
My main account was indeed also the admin account for the server. If I had seen that script, that would have made this server vulnerable to the attack - I may have and we just missed it out of sheer luck. That and the backup account have both been moved to alternate accounts - I’m now following security best practices by separating out admin and every day use users.
The only practical change here is that I now have to log in as a separate user to approve applications and if I feel like changing the sidebar. I’ll live. :)
