Wholesale Floorplanning Finance Cross-site Scripting

In Apak Wholesale Floorplanning Finance 6.31.8.3 and 6.31.8.5, an attacker can send an authenticated POST request with a malicious payload to /WFS/agreementView.faces allowing a stored XSS via the mainForm:loanNotesnotes:0:rich_text_editor_note_text parameter in the Notes section. Although versions 6.31.8.3 and 6.31.8.5 are confirmed to be affected, all versions with the vulnerable WYSIWYG editor in the Notes section are likely affected. (2019-10-31, CVE-2019-17551)

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>