Would output: fix our previous example using this method: '.
Htmlspecialchars will convert any "HTML special characters" into their HTML encodings, meaning they will then not be processed as standard HTML. They are useful when saving or outputting client input. PHPs Filter Functions allow the input data to the php script to be sanitized or validated in many ways. PHP provides a few ways to escape output depending on the context. Therefore it is a best practice to always escape output. Keep in mind that even in the simplest applications data can be moved around and it will be hard to keep track of all sources. When outputting any of these values, escape them so they will not be evaluated in an unexpected way. Every GET parameter, POST or PUT content, and cookie value could be anything at all, and should therefore be validated. SolutionĪs a general rule, never trust input coming from a client. ![]() The 3rd party JavaScript will run and the user will see "I'm running" on the web page. ![]() If an unchecked GET parameter contains then the output of the PHP script will be: If input includes HTML or JavaScript, remote code can be executed when this content is rendered by the web client.įor example, if a 3rd party side contains a JavaScript file: // Īnd a PHP application directly outputs a string passed into it: '. Any web application might expose itself to XSS if it takes input from a user and outputs it directly on a web page. ProblemĬross-site scripting is the unintended execution of remote code by a web client. Cross-posting this as a consolidated reference from the SO Documentation beta which is going offline.
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