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This time we're using textContent to ensure the data is properly encoded. Or you can use createElement() to dynamically create document elements Do NOT use document.write() on dynamically generated data as itĭocument.getElementById("scriptedWrite").innerText += clientSideUntrustedInputOldStyle Put the injected, untrusted data into the scriptedWrite div tag. InjectedData.getAttribute("data-untrustedinput") Var injectedData = document.getElementById("injectedData") For example: untrustedInput = "alert(1)" The safest way to insert values is to place the value in a data attribute of a tag and retrieve it in your JavaScript. There may be times you want to insert a value into JavaScript to process in your view. This should never be used in combination with untrusted input as this will expose an XSS vulnerability.

This variable includes some characters which are used in XSS attacks, namely. HTML encoding takes characters such as view outputs the contents of the untrustedInput variable.

Untrusted data is any data that may be controlled by an attacker, HTML form inputs, query strings, HTTP headers, even data sourced from a database as an attacker may be able to breach your database even if they cannot breach your application.īefore putting untrusted data inside an HTML element ensure it's HTML encoded. Never put untrusted data into your HTML input, unless you follow the rest of the steps below. Developers should use the following prevention steps to avoid introducing XSS into their application.

Protecting your application against XSSĪt a basic level XSS works by tricking your application into inserting a tag into your rendered page, or by inserting an On* event into an element. XSS vulnerabilities generally occur when an application takes user input and outputs it to a page without validating, encoding or escaping it. When other users load affected pages the attacker's scripts will run, enabling the attacker to steal cookies and session tokens, change the contents of the web page through DOM manipulation or redirect the browser to another page. Cross-Site Scripting (XSS) is a security vulnerability which enables an attacker to place client side scripts (usually JavaScript) into web pages.