C H A P T E R  4

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Preventing Cross-Site Scripting

We continue our survey of secure PHP programming by discussing the threat to your users' data posed by a highly specialized version of dangerous user input known as cross-site scripting (XSS). Unlike SQL injection (discussed in Chapter 3), which attempts to insert malicious SQL instructions into a database query that is executed out of public view, XSS attempts to insert malicious markup or JavaScript code into values that are subsequently displayed in a web page. This malicious code attempts to take advantage of a user's trust in a website, by tricking him (or his browser) into performing some ...

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