source: https://www.securityfocus.com/bid/5847/info

Apache is reported to be vulnerable to cross site scripting attacks. This vulnerability is due to the SSI error pages of the webserver not being properly sanitized of malicious HTML code.

Attacker-supplied HTML and script code may be executed on a web client visiting the malicious link in the context of the webserver.

Attacks of this nature may make it possible for attackers to manipulate web content or to steal cookie-based authentication credentials. It may be possible to take arbitrary actions as the victim user.

http://%3CIMG%20SRC%3D%22%22%20ONERROR%3D%22alert%28document%2Ecookie%29%22
%3E.apachesite.org/raise_404