Open redirection vulnerabilities are like an open door for hackers. They let attackers trick users into landing on shady websites, from phishing scams to malware traps. If you’re a cybersecurity pro or an ethical hacker, spotting these weaknesses is a must to keep web apps secure. In this guide, I’m sharing the top 15 ways to find open redirection flaws, packed with practical tips to level up your penetration testing game. Whether you’re just starting out or have years of experience, these tricks will help you catch open redirects and lock down your systems.
Table of Contents
What Exactly Are Open Redirection Vulnerabilities?
A web app lets users click a link, but instead of going to a trusted page, they’re sent to a malicious site. That’s an open redirection vulnerability in action. It happens when an app doesn’t properly check where a redirect is pointing, letting attackers sneak in external URLs. By learning the techniques in this post, you can spot these risks and stop them in their tracks, keeping users safe.
Why You Need to Hunt for Open Redirects
While open redirection may seem harmless at first, they can be leveraged for various attacks:
- Attackers perform phishing attacks when they create deceptive login interfaces which duplicate real website pages to trick users into providing their authentication details.
- User credentials become vulnerable when the malicious attacker maintains control over the redirected page.
- Some authentication protocols transfer authentication tokens through URLs but these tokens become vulnerable to attackers who intercept them.
- Attackers can use open redirects as a platform to execute unauthorized access through collaboration with other attacks for instance SSRF and XSS.
- A malicious actor who exploits OAuth & SSO redirections steers users to unauthorized authorization endpoints to hijack authentication systems.
1. Common Parameter Fuzzing
Fuzzing URL parameters like ?redirect=, ?url=, or ?next= is a go-to method. Test these parameters by injecting external URLs (e.g., https://example.com). If the application redirects without validation, you’ve found a vulnerability. Use tools like Burp Suite to automate fuzzing and save time.
https://example.com/redirect?url=https://malicious.comIf this URL redirects you to malicious.com, the site is vulnerable.
2. Using “//” to Bypass Filters
Some applications filter http:// or https:// but miss //. Inject //malicious.com into a redirect parameter. If the browser interprets it as a protocol-relative URL, it may redirect to the attacker’s site. This technique is simple yet effective for finding open redirects.
https://example.com/redirect?url=//malicious.comBrowsers treat //malicious.com as https://malicious.com, leading to an external redirection.
3. Using @ to Trick the System
The @ symbol can confuse URL parsers. For example, appending @malicious.com to a legitimate domain (e.g., https://example.com@malicious.com) might redirect to the malicious site. Test this on login or redirect endpoints to uncover hidden vulnerabilities.
Some sites only check the first part of the URL and ignore everything after @.
https://example.com/redirect?url=https://example.com@malicious.comEven though example.com is present, the browser sends you to malicious.com.
4. Appending Path Traversal (../)
Path traversal sequences like ../ can manipulate redirect paths. Try injecting ../malicious.com into a parameter. If the application fails to sanitize the input, it may redirect to an unintended destination. This method works well with poorly configured servers.
https://example.com/redirect?url=/../malicious.comThis tricks the system into redirecting to malicious.com.
5. URL Shorteners to Bypass Restrictions
URL shorteners like Bit.ly or TinyURL can mask malicious URLs. Inject a shortened link into a redirect parameter. If the application allows the redirect, it’s vulnerable. This technique is popular among attackers and a must-test for pentesters.
https://example.com/redirect?url=https://bit.ly/evilThe site may allow redirection to short links, which will then take users to the malicious website.
6. Bypassing “Allow List” with Subdomains
Some applications use allow lists to restrict redirects to trusted domains. Test subdomains like subdomain.example.com or example.com.malicious.com. If the application doesn’t validate subdomains properly, you can bypass the allow list.
https://example.com/redirect?url=https://sub.example.com@malicious.comEven though example.com appears in the URL, it actually leads to malicious.com.
7. Encoding Variations (URL Encoding)
URL encoding (e.g., %68%74%74%70%3A%2F%2F) can evade filters. Encode a malicious URL and inject it into a parameter. If the application decodes and redirects, it’s vulnerable. Test multiple encoding layers for thoroughness.
https://example.com/redirect?url=%68%74%74%70%73%3A%2F%2Fmalicious.comThis encodes https://malicious.com, making it harder for filters to detect.
8. Using # Fragment to Trick Validation
The # fragment can bypass validation checks. Inject a URL like https://example.com#malicious.com. If the application processes the fragment as a redirect, you’ve found a flaw. This method is subtle but effective.
https://example.com/redirect?url=https://example.com#https://malicious.comSince everything after # is ignored by the server, the browser still goes to malicious.com.
9. Injecting NULL Byte (%00)
NULL bytes (%00) can terminate strings in some systems. Inject %00 followed by a malicious URL (e.g., ?redirect=example.com%00malicious.com). If the application ignores everything after %00, it may redirect to the malicious site.
https://example.com/redirect?url=https://example.com%00https://malicious.comThe system might only check example.com, but the browser follows malicious.com.
10. Path Injection in Redirection
Inject paths like /redirect?url=malicious.com into parameters. If the application appends the input to a base URL without validation, it may redirect to the injected path. Test this on APIs and legacy endpoints.
https://example.com/redirect?url=/safe/../malicious.comThe system might allow malicious.com by mistake.
11. Bypassing JavaScript-Based Redirections
Some redirects rely on JavaScript (e.g., window.location). Analyze the code for weak validation and inject malicious URLs. Tools like Chrome DevTools can help you debug and identify vulnerabilities.
12. Exploiting OAuth Redirection Endpoints
OAuth endpoints often use redirect_uri parameters. Test these by injecting external URLs. Misconfigured OAuth flows are a common source of open redirects, especially in social login systems.
13. Parameter Pollution (Duplicate Parameters)
HTTP Parameter Pollution (HPP) involves injecting duplicate parameters (e.g., ?url=example.com&url=malicious.com). If the application processes the last parameter without validation, it may redirect to the malicious URL.
https://example.com/redirect?url=https://example.com&url=https://malicious.comSome systems only process the last value, sending users to malicious.com.
14. HTTP Referer Header Manipulation
Some applications trust the Referer header for redirects. Use a proxy like Burp Suite to manipulate the header and inject a malicious URL. If the application redirects based on the tampered header, it’s vulnerable.
Change the Referer in Burp Suite:
Referer: https://malicious.comThe site might trust Referer and redirect users.
15. Finding Open Redirects via SSRF (Server-Side Request Forgery)
Server-Side Request Forgery (SSRF) can trigger open redirects. Craft requests to internal endpoints with redirect parameters. If the server follows the redirect to an external URL, you’ve uncovered a vulnerability.
Best tool for automating Open Redirect Testing
- Burp Suite → Modify requests manually
- GF Patterns (
gf redirect) → Extract redirect vulnerabilities - ParamSpider → Find hidden parameters
- Arjun → Fuzz URL parameters
- Nuclei → Scan for predefined redirect vulnerabilities (
nuclei -t cves/open-redirects.yaml)
Conclusion
Mastering the top 15 ways to find open redirection vulnerabilities equips you to secure web applications and outsmart attackers. From parameter fuzzing to SSRF, these techniques are your toolkit for ethical hacking success. Start testing today and join the cybersecurity community in making the web safer.
Share your bypass tips in the comments!
Hii
This side surender
I need one website in redirect
For testing purpose you can use vulnweb.com