The remote host is vulnerable to a Cross-Site Scripting (XSS) attack.
The remote host is running a vulnerable version of Acme thttpd. It is reported that this version of thttpd fails to check URLs for the presence of script commands when generating error pages. An attacker may craft links containing scripting code in order to execute code within the context of the website.
Upgrade to thttpd 2.21 or higher.