This difference makes JavaScript encoding a less viable weapon in our fight against XSS. Additionally, the website's scripts might perform validation or other processing of data that must be accommodated when attempting to exploit a vulnerability. There will be situations where you use a URL in different contexts. Based on our research summarized in the Acunetix Web Application Vulnerability Report, DOM-based cross-site scripting is not very common such vulnerabilities exist only in approximately 1.2% of analyzed web applications. Therefore, the primary recommendation is to avoid including untrusted data in this context. If you have to use user input on your page, always use it in the text context, never as HTML tags or any other potential code. The document.write sink works with script elements, so you can use a simple payload, such as the one below: Note, however, that in some situations the content that is written to document.write includes some surrounding context that you need to take account of in your exploit. Its easy to make mistakes with the implementation so it should not be your primary defense mechanism. DOM-based XSS simply means a cross-site scripting vulnerability that occurs in the DOM ( Document Object Model) of your site rather than in HTML. Variables should only be placed in a CSS property value. This is a Safe Sink and will automatically CSS encode data in it. There are also TrustedScript and TrustedScriptURL objects for other sensitive sinks. You should apply HTML attribute encoding to variables being placed in most HTML attributes. However, depending on the tag which innerText is applied, code can be executed. HTML tag elements are well defined and do not support alternate representations of the same tag. Cross-Site Scripting (XSS) is a security vulnerability that allows an attacker to inject malicious code into a web page viewed by other users. Get started with Burp Suite Professional. \u0064\u006f\u0063\u0075\u006d\u0065\u006e\u0074, \u0077\u0072\u0069\u0074\u0065\u006c\u006e, "\u0048\u0065\u006c\u006c\u006f\u0020\u0057\u006f\u0072\u006c\u0064", "\u0061\u006c\u0065\u0072\u0074\u0028\u0031\u0031\u0029", "url(<%=ESAPI.encoder().encodeForJavascript(ESAPI.encoder().encodeForURL(companyName))%>)", '<%=ESAPI.encoder().encodeForJavascript(ESAPI.encoder().encodeForURL(userRelativePath))%>', "<%= Encode.forJavaScript(untrustedData) %>", "<%=ESAPI.encoder().encodeForJavascript(untrustedData)%>", "customFunction('<%=doubleJavaScriptEncodedData%>', y)", //HTML encoding is happening in JavaScript, "javascript:myFunction('<%=untrustedData%>', 'test');", "javascript:myFunction('<%=ESAPI.encoder().encodeForJavascript(ESAPI.encoder().encodeForURL(untrustedData)) %>', 'test');",
