source: https://www.securityfocus.com/bid/27697/info

Serendipity Freetag-plugin is prone to a cross-site scripting vulnerability because it fails to sufficiently sanitize user-supplied data.

Exploiting this issue could allow an attacker to steal cookie-based authentication credentials and to launch other attacks.

This issue affects Serendipity Freetag-plugin 2.95; prior versions may also be affected.

http://www.example.com/plugin/tag/%3Cdiv%20style=[XSS]