This article is a part of our Vulnerability Database (back to index)
Cross-site Scripting occurrences in Teams
The Microsoft Teams online service contains a stored cross-site scripting vulnerability in the displayName parameter that can be exploited on Teams clients to obtain sensitive information such as authentication tokens and to possibly execute arbitrary commands. This vulnerability was fixed for all Teams users in the online service on or around October 2020. (2020-12-09, CVE-2020-10146)
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>