Nisarg Shah
September 1, 2025
5 Minutes read
How to Identify and Fix Open Redirect Vulnerabilities
Open redirect vulnerabilities are one of the most underestimated risks in web applications. At first glance, they may look harmless; after all, it’s just a redirect. But attackers know how to exploit this flaw to trick users, steal credentials, or drive traffic to malicious websites, all while hiding behind your trusted source.
In this blog post, we will help you understand:
- What open redirects are
- Why they are dangerous
- How to detect them
- How to fix and prevent them
- Real-world examples and statistics
What Is an Open Redirect Vulnerability?
An open redirect occurs when a web application allows users to be redirected to any external URL without proper validation. This means an attacker can craft a link that looks safe but silently sends the user to a malicious site.
Example
Let’s say you have the following logout URL:
https://example.com/logout?redirect=https://malicious-site.com
When clicked, the user sees example.com in the link which looks safe and trustworthy, but behind the scenes they are forwarded to malicious-site.com. This technique is often used in phishing campaign to trick users into entering credentials on a fake login page.
Why Open Redirects Are Dangerous
Open redirects may look like a small bug, but they can cause big damage:
- Phishing attacks: Redirecting users to fake login pages that steal usernames and passwords.
- Social engineering: Tricking users into visiting malware-infected or scam websites.
- Brand trust erosion: Attackers misuse your domain, reducing trust in your services.
- Search engine manipulation: Redirects can be exploited to manipulate search engine rankings.
Even if your website is not directly compromised, open redirect bugs give attackers a tool to abuse your reputation.
Real-World Data
- The OWASP Top 10 still lists unvalidated redirects as a recurring problem in web applications.
- The 2025 Verizon Data Breach Investigations Report (DBIR) found that over 20% of phishing emails analyzed in 2024 involved open redirect abuse.
- Major platforms like Google, Facebook, and LinkedIn have paid bug bounties for open redirect vulnerabilities reported on their platforms.
If tech giants aren’t immune, no business should overlook this risk.
How to Identify Open Redirects in Your Application
Identifying open redirect vulnerabilities requires a combination of manual testing, automated tools, and reviewing your codebase.
1. Manual Testing
Try visiting or modifying URLs in your application that include parameters like ?
redirect=, ?url=, ?next=, or ?returnTo=.
Example test case:
https://yourapp.com/login?next=https://evil.com
If you are redirected to the external site without any warning or validation, then your application is likely vulnerable.
2. Use Automated Security Scanners
There are several tools that can help automate this process:
- Burp Suite – Detects open redirects during vulnerability scans.
- OWASP ZAP (Zed Attack Proxy) – Free tool for identifying web security issues.
- Custom Scripts – Build crawlers to identify parameters that perform redirection.
3. Review the Code
Look for code that performs redirection based on user input:
Example (Vulnerable Python code):
def login(request):
next_url = request.GET.get(‘next’)
return redirect(next_url)
This code takes a URL from the user and redirects to it with no validation. That is dangerous.
How to Fix Open Redirect Vulnerabilities
1. Restrict Redirects to Internal Domains
Ensure that the redirection destination is part of your application’s domain.
Example (Safe):
from urllib.parse import urlparse
def is_safe_url(url, allowed_host):
parsed_url = urlparse(url)
return parsed_url.netloc == ” or parsed_url.netloc == allowed_host
def login(request):
next_url = request.GET.get(‘next’)
if is_safe_url(next_url, ‘yourapp.com’):
return redirect(next_url)
return redirect(‘/dashboard’)
2. Use a Whitelist of Approved URLs
Allow redirects only to a known set of URLs or paths.
WHITELIST = [‘/home’, ‘/dashboard’, ‘/settings’]
if next_url in WHITELIST:
return redirect(next_url)
3. Use Relative Paths Only
Allow redirection only to internal paths, not full external URLs.
if next_url.startswith(‘/’):
return redirect(next_url)
else:
return redirect(‘/error’)
4. Avoid User-Controlled Redirects When Possible
Instead of relying on URL parameters, store redirect destinations in session variables or handle them in the backend.
Best Practices for Preventing Open Redirects
- Validate and sanitize all redirect parameters.
- Never trust input directly from the user without checking it first.
- Avoid using full URLs in redirection logic; use relative paths instead.
- Educate your development teams about this issue during code reviews.
- Include open redirect tests in your CI/CD pipeline and security scans.
- Use HTTP headers such as Content-Security-Policy and Referrer-Policy to reduce phishing impact.
Real-World Example in Action
Imagine a banking site with this login URL:
https://bank.com/login?next=https://bank-login-help.com
If that URL redirects you to an external site that looks like your login page but is run by an attacker, users could unknowingly give away their banking credentials. That’s exactly how open redirect vulnerabilities are used in real attacks.
Final Thoughts
Open redirects vulnerabilities are often overlooked because they don’t directly expose data. But attackers use them as stepping stones for phishing, fraud, and brand abuse.
The fix if straightforward:
- Validate redirect destinations
- Use whitelists or relative paths.
- Remove unnecessary redirect parameters
By tightening these checks, you can protect your users and safeguard your domain’s reputation.
Next-Step: Run an automated security scan (with tools like Burp Suite or OWASP ZAP) against your web application today. If you discover redirect parameters, patch them immediately to protect your users and your brand.
Secure your web application today. Schedule a vulnerability assessment with our security experts to identify and fix open redirect risks before attackers do.
