The remote host is vulnerable to a 'file upload' flaw.
The remote host is running FCKeditor plugin for PHPNuke. FCKeditor is a web-based document editor. This version of FCKeditor is vulnerable to a flaw in the way that it verifies file extensions for file uploads. An attacker exploiting this flaw would be able to upload potentially malicious code to the web server that might, under certain circumstances, be executable via a remote HTTP request.
Upgrade or patch according to vendor recommendations.