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GHSA-m64q-4jqh-f72f
No affected components available
Summary
A stored XSS vulnerability in Excalidraw's web embeddable component. This allows arbitrary JavaScript to be run in the context of the domain where the editor is hosted.
Poc
Inserting an embed with the below url (can be copy/pasted onto canvas to insert as embed) will log 42 to the console:
https://gist.github.com/vv=v<script>console.log(42)</script>
Details
There were two vectors. One rendering untrusted string as iframe's srcdoc without properly sanitizing against HTML injection. Second by improperly sanitizing against attribute HTML injection. This in conjunction with allowing allow-same-origin sandbox flag (necessary for several embeds) resulted in the XSS.
Former was fixed by no longer rendering unsafe srcdoc content verbatim, and instead strictly parsing the supplied content and constructing the srcdoc manually. The latter by sanitizing properly.
The allow-same-origin flag is now also set only in cases that require it, following the principle of least privilege.
Impact
This is a cross site scripting vulnerability, for more information, please see: https://portswigger.net/web-security/cross-site-scripting
Two npm @excalidraw/excalidraw stable version releases were affected (0.16.x, 0.17.x), and both are now patched.
The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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