This article is a part of our Vulnerability Database (back to index)
Cross-site Scripting occurrences in Owncast
Owncast is an open source, self-hosted live video streaming and chat server. In affected versions inline scripts are executed when Javascript is parsed via a paste action. This issue is patched in 0.0.9 by blocking unsafe-inline Content Security Policy and specifying the script-src. The worker-src is required to be set to blob for the video player. (2021-12-14, CVE-2021-39183)
Why Cross-site Scripting can be dangerous
Cross site scripting is an attack where a web page executes code that is injected by an adversary. It usually appears, when users input is presented. This attack can be used to impersonate a user, take over control of the session, or even steal API keys.
The attack can be executed e.g. when you application injects the request parameter directly into the HTML code of the page returned to the user:
https://server.com/confirmation?message=Transaction+Complete
what results in:
<span>Confirmation: Transaction Complete</span>
In that case the message can be modified to become a valid Javascript code, e.g.:
https://server.com/confirmation?message=<script>dangerous javascript code here</script>
and it will be executed locally by the user's browser with full access to the user's personal application/browser data:
<span>Confirmation: <script>dangerous javascript code here</script></span>