Reflected XSS

docs/misc/owasp.md

@@ -292,7 +292,68 @@ LDAP injection is a severe security risk, and understanding how it works and how
 
 ---
 
-## Reflected XSS
+## Reflected Cross-Site Scripting (XSS)
+
+
+Reflected Cross-Site Scripting (XSS) is a type of web vulnerability that occurs when an application takes user input and returns it directly to the browser without proper validation or encoding. This vulnerability can allow attackers to inject malicious scripts into web pages viewed by other users, leading to various potential exploits like identity theft, data breaches, and other malicious activities.
+
+### Understanding Reflected XSS
+
+Reflected XSS, also known as non-persistent XSS, occurs when malicious script injected by an attacker is reflected off the web server, such as in an error message, search result, or any other response that includes some or all of the input sent to the server as part of the request.
+
+#### Example:
+
+Consider a simple Java servlet example that reads a parameter from the HTTP request and reflects it back in the HTTP response:
+
+```java
+import java.io.IOException;
+import javax.servlet.ServletException;
+import javax.servlet.http.HttpServlet;
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+public class ReflectedXSSExample extends HttpServlet {
+    protected void doGet(HttpServletRequest request, HttpServletResponse response)
+            throws ServletException, IOException {
+        String userInput = request.getParameter("userInput");
+        response.getWriter().write("You entered: " + userInput);
+    }
+}
+```
+
+In this code snippet, the servlet takes a `userInput` parameter from the HTTP request and echoes it directly back to the user in the HTTP response without any validation or encoding. If an attacker sends a malicious script as the `userInput` parameter, it will be reflected back to the user and executed in the user's browser.
+
+### Mitigating Reflected XSS
+
+Preventing Reflected XSS involves validating, sanitizing, or escaping every piece of data that can be manipulated by end users.
+
+#### Input Validation:
+- Validate input to ensure it conforms to expected formats.
+- Reject any input that does not strictly conform to specifications.
+
+#### Output Encoding:
+- Encode data when you are outputting it to the browser to prevent malicious data from being executed as script.
+- Use encoding libraries or built-in functions to ensure data is correctly encoded.
+
+#### Content Security Policy (CSP):
+- Implement a Content Security Policy to restrict the sources and types of content that can be executed on your pages.
+- Ensure your CSP is strict and does not allow unsafe inline script or other dangerous content.
+
+#### Use Safe APIs and Libraries:
+- Use APIs and libraries that automatically escape user input for you.
+- Ensure the libraries and frameworks you use are up-to-date and follow best security practices.
+
+#### Regular Security Testing:
+- Conduct regular security testing to identify and fix potential XSS vulnerabilities.
+- Utilize automated scanning tools and manual testing to ensure comprehensive coverage.
+
+#### Education:
+- Educate developers about the risks associated with XSS and how to prevent them.
+- Keep up-to-date with the latest advancements in web security to ensure your protection measures are effective.
+
+By following these best practices, developers can significantly reduce the risk of Reflected XSS vulnerabilities in their Java web applications, contributing to a more secure and reliable application environment.
+
+Reflected XSS is a serious security risk that can have severe consequences if not adequately mitigated. Understanding the risks, knowing how to prevent them, and implementing secure coding practices are crucial steps in developing secure Java web applications. This document provides a foundational understanding of Reflected XSS, an illustrative example, and various preventative measures to mitigate this type of vulnerability.