Fortinac Cross-site Scripting

An improper neutralization of input vulnerability in FortiNAC before 8.7.2 may allow a remote authenticated attacker to perform a stored cross site scripting attack (XSS) via the UserID of Admin Users. (2020-09-24, CVE-2020-12816)

An Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting") in Fortinet FortiNAC 8.3.0 to 8.3.6 and 8.5.0 admin webUI may allow an unauthenticated attacker to perform a reflected XSS attack via the search field in the webUI. (2019-08-23, CVE-2019-5594)

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>