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(URGENT) Lemmy has an XSS vulnerability in the tagline, the sidebar and in the legal information field
(sh.itjust.works)
DO NOT OPEN THE "LEGAL" PAGE
lemmy.world is a victim of an XSS attack right now and the hacker simply injected a JavaScript redirection into the sidebar.
It appears the Lemmy backend does not escape HTML in the main sidebar. Not sure if this is also true for community sidebars.
EDIT:
the exploit is also in the tagline that appears on top of the main feed for status updates, like the following one for SDF Chatter:
EDIT 2:
The legal information field also has that exploit, so that when you go to the "Legal" page it shows the HTML unescaped, but fortunately (for now) he's using double-quotes.
"legal_information":" ![\" onload=\"if(localStorage.getItem(`h`) != `true`){document.body.innerHTML = `\u003Ch1\u003ESite has been seized by Reddit for copyright infringment\u003C\u002Fh1\u003E`; setTimeout(() =\u003E {window.location.href = `https:\u002F\u002Flemmy.world\u002Fpictrs\u002Fimage\u002F7aa772b7-9416-45d1-805b-36ec21be9f66.mp4`}, 10000)}\"](https:\u002F\u002Flemmy.world\u002Fpictrs\u002Fimage\u002F66ca36df-4ada-47b3-9169-01870d8fb0ac.png \"lw\")
The reason it's perceived that way is because code injection in user input, is (one of) the most obvious, well-known, and easiest attacks to do, while at the same time being super easy to prevent.
It is one of the most well known, but it also is easy to miss, evidently from how often it happens despite it being very well known.
It's very easy to fix once it's known, but it is easy to go unnoticed.
Unless you somehow think that most app developers are incompetent, in which case I ask again: show me your better version.
I can confidently say that in not a single company project I did frontend development for did I ever leave user input unsanitized.
But I did not ever create a Lemmy like project, that is true.
If you are doubting that this is one of the most frequently occurring security issues, I urge to search the web about it. It's very easy to verify my claim.