Variables should not be interpreted as code instead of text. When you need to safely display data exactly as a user types it in, output encoding is recommended. Output encoding and HTML sanitization help address those gaps. However, no framework is perfect and security gaps still exist in popular frameworks like React and Angular. Frameworks make it easy to ensure variables are correctly validated and escaped or sanitised. Any variable that does not go through this process is a potential weakness. Ensuring that all variables go through validation and are then escaped or sanitized is known as perfect injection resistance. Thus, all variables in a web application needs to be protected. In order for an XSS attack to be successful, an attacker must be able to to insert and execute malicious content in a webpage. OWASP will be producing framework specific cheatsheets for React, Vue, and Angular. There will be times where you need to do something outside the protection provided by your framework, which means that Output Encoding and HTML Sanitization can be critical. When you use a modern web framework, you need to know how your framework prevents XSS and where it has gaps. Out of date framework plugins or components.Angular’s bypassSecurityTrustAs* functions. React cannot handle javascript: or data: URLs without specialized validation.React’s dangerouslySetInnerHTML without sanitising the HTML.escape hatches that frameworks use to directly manipulate the DOM.However, developers need to know that problems can occur if frameworks are used insecurely, such as: Framework Security ¶įortunately, applications built with modern web frameworks have fewer XSS bugs, because these frameworks steer developers towards good security practices and help mitigate XSS by using templating, auto-escaping, and more. Since no single technique will solve XSS, using the right combination of defensive techniques will be necessary to prevent XSS. This cheatsheet contains techniques to prevent or limit the impact of XSS. XSS attacks are serious and can lead to account impersonation, observing user behaviour, loading external content, stealing sensitive data, and more. Since then, the term has widened to include injection of basically any content. Originally this term was derived from from early versions of the attack that were primarily focused on stealing data cross-site. This cheat sheet helps developers prevent XSS vulnerabilities.Ĭross-Site Scripting (XSS) is a misnomer. Insecure Direct Object Reference PreventionĬross Site Scripting Prevention Cheat Sheet ¶ Introduction ¶ Output Encoding for “JavaScript Contexts” * Private constructor to prevent this class from being instantiated.Output Encoding for “HTML Attribute Contexts” Public static String encodeURIComponent(String s) * with JavaScript's encodeURIComponent function. * Encodes the passed String as UTF-8 using an algorithm that's compatible Public static String decodeURIComponent(String s) * s The UTF-8 encoded String to be decoded * JavaScript's decodeURIComponent function. * Decodes the passed UTF-8 String using an algorithm that's compatible with * Utility class for JavaScript compatible UTF-8 encoding and decoding. This is the class I came up with in the end: import java.io.UnsupportedEncodingException This program outputs: URLEncoder.encode returns %22A%22+B+%C2%B1+%22Ĭlose, but no cigar! What is the best way of encoding a UTF-8 string using Java so that it produces the same output as JavaScript's encodeURIComponent?ĮDIT: I'm using Java 1.4 moving to Java 5 shortly. Public static void main(String args) throws UnsupportedEncodingException Here's my little test Java program: import java.io.UnsupportedEncodingException If I enter the following JavaScript statement in Firebug: encodeURIComponent('"A" B ± "') I've been experimenting with various bits of Java code trying to come up with something that will encode a string containing quotes, spaces and "exotic" Unicode characters and produce output that's identical to JavaScript's encodeURIComponent function.
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