Fixing Reflected Cross-Site Scripting (Reflected XSS)

Vulnerability Analysis

Reflected Cross-Site Scripting occurs when an application takes user input from a request parameter (such as a search input or error message) and returns it in the immediate HTML response without escaping it, leading to script execution.

How it is Detected

Detected by sending test query parameters containing script tokens and checking if the response outputs the exact unescaped input.

Remediation Guidelines

Always escape output variables in the response context. Implement strict Content Security Policy (CSP) parameters to prevent unauthorized scripts.

Remediation Script (Node.js / Express (escaping))

// SECURE REMEDIATION: Escaping request parameters
const escapeHtml = require('escape-html');
app.get('/search', (req, res) => {
  const query = req.query.q;
  res.send(`Search results for: ${escapeHtml(query)}`);
});