Fixing Open Redirect Vulnerability

Vulnerability Analysis

Open Redirect vulnerabilities occur when a web application accepts a user-controlled parameter specifying a destination URL and redirects the browser to that URL without validating if it belongs to a trusted domain.

How it is Detected

Identified by modifying redirect parameters (like ?next= or ?url=) to point to external destinations and checking if the application routes traffic there.

Remediation Guidelines

Avoid user-controlled redirection targets. If required, strictly whitelist allowed redirect destinations or validate that the path starts with a local root slash (/).

Remediation Script (Node.js / Express (safe redirect))

// SECURE REMEDIATION: Whitelisting relative paths
app.get('/login', (req, res) => {
  const target = req.query.next || '/';
  if (target.startsWith('/') && !target.startsWith('//')) {
    res.redirect(target);
  } else {
    res.redirect('/');
  }
});