There are two types of web pages, static and dynamic. A static page has fixed content the browser simply displays whatever was in the page the server generated. Static pages are not affected by this vulnerability. Dynamic pages contain both fixed content and executable content. When the browser receives a dynamic page, it processes the executable content in order to determine how to display the fixed content.
Dynamic pages provide for a much richer user experience.
They allow web pages to be animated, to tailor how the content is displayed based on each user s preferences, and so forth. However, through Cross-Site Scripting, a malicious user might be able to introduce additional executable content, in the form of script, into a dynamic page. When such a page was sent to the browser, the script would execute on the user s computer with the permissions appropriate to the web site. Actually, it happens all the time. Suppose you visited a search page on a web site.