23.3.1. Cross-site scripting with PHP-Nuke

A CSS vulnerability is caused by the failure of a site to validate user input before returning it to the client s web-browser. The essence of cross-site scripting is that an intruder causes a legitimate web server to send a page to a victim's browser that contains malicious script or HTML of the intruder's choosing. The malicious script runs with the privileges of a legitimate script originating from the legitimate web server (see Cross-Site Scripting Vulnerabilities). By failing to validate user input, the vulnerable site makes it possible for a malicious user to execute ("inject") a script in the context of that site's process.

Here are some known examples of cross-site scripting with PHP-Nuke:

As you can see from the above examples, the only remedy to cross-site scripting problems is to write PHP code that validates user input (or, if you are the "viewer", disable scripting altogether, although even this will not prevent the injection of malicious HTML, see Cross-Site Scripting Vulnerabilities).


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Chris Karakas, Maintainer PHP-Nuke HOWTO