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Cross-site Scripting occurrences in Onedev
Onedev is an open source, self-hosted Git Server with CI/CD and Kanban. During CI/CD builds, it is possible to save build artifacts for later retrieval. They can be accessed through OneDev's web UI after the successful run of a build. These artifact files are served by the webserver in the same context as the UI without any further restrictions. This leads to Cross-Site Scripting (XSS) when a user creates a build artifact that contains HTML. When accessing the artifact, the content is rendered by the browser, including any JavaScript that it contains. Since all cookies (except for the rememberMe one) do not set the HttpOnly flag, an attacker could steal the session of a victim and use it to impersonate them. To exploit this issue, attackers need to be able to modify the content of artifacts, which usually means they need to be able to modify a project's build spec. The exploitation requires the victim to click on an attacker's link. It can be used to elevate privileges by targeting admins of a OneDev instance. In the worst case, this can lead to arbitrary code execution on the server, because admins can create Server Shell Executors and use them to run any command on the server. This issue has been patched in version 7.3.0. Users are advised to upgrade. There are no known workarounds for this issue. (2022-09-13, CVE-2022-39207)
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>