source: http://www.securityfocus.com/bid/34688/info

Flat Calendar is prone to an HTML-injection vulnerability because it fails to sufficiently sanitize user-supplied data.

Attacker-supplied HTML or JavaScript code could run in the context of the affected site, potentially allowing the attacker to steal cookie-based authentication credentials and to control how the site is rendered to the user; other attacks are also possible.

"><script>alert("ZoRLu")</script>