source: https://www.securityfocus.com/bid/41961/info

Joomla! FreiChat component is prone to an HTML-injection vulnerability because it fails to properly sanitize user-supplied input before using it in dynamically generated content.

Successful exploits will allow attacker-supplied HTML and script code to run in the context of the affected browser, potentially allowing the attacker to steal cookie-based authentication credentials or to control how the site is rendered to the user. Other attacks are also possible.

Versions prior to FreiChat 2.1.2 are vulnerable. 

<script>alert('hello')</script>