source: http://www.securityfocus.com/bid/12568/info

A vulnerability is reported to exist in osCommerce that may allow a remote user to launch cross-site scripting attacks.

This issue could permit a remote attacker to create a malicious URI link that includes hostile HTML and script code. If this link were to be followed, the hostile code may be rendered in the web browser of the victim user. This would occur in the security context of the affected Web site and may allow for theft of cookie-based authentication credentials or other attacks.

This vulnerability is reported to exist in osCommerce version 2.2-MS2, other versions might also be affected. 

http://www.example.com/contact_us.php?&name=1&email=1&enquiry=%3C/textarea%3E%3Cscript%3Ealert('w00t');%3C/script%3E