Exposing OTP Bypass Vulnerabilities: Step-by-Step Bug Bounty Case Study
Bug Bounty
In the ever-evolving landscape of cybersecurity, the protection of user data is paramount. One common security measure implemented by many platforms is the use of One-Time Passwords (OTPs) for user verification. However, even such mechanisms can sometimes have vulnerabilities that, if exploited, could lead to unauthorized access to user accounts. My recent discovery of an OTP bypass vulnerability in a website’s login process allows attackers to access the website without a valid OTP, which allowed me to gain access. Suppose the website is http://www.example.com.
What is an OTP Bypass Vulnerability?
An OTP bypass vulnerability occurs when the OTP verification mechanism, which is designed to secure the login process, can be circumvented. This can happen due to improper validation or other flaws in the implementation of the OTP system. In this case, this vulnerability allowed attackers to bypass OTP verification entirely.
How I Exploit the Vulnerability
Navigate to the Website: I visit the website and navigate to the login screen.
Enter a Mobile Number: On the login screen, I enter a mobile number and proceed to the OTP verification step. This is where the vulnerability comes into play.
Use a Proxy Tool: I use Burp Suite to intercept the OTP request. This tool allows me to monitor and modify network traffic between my browser and the server.
Intercept the OTP Request: When I reach the OTP verification step, I enter a random OTP, such as ‘0000’. Then, I intercept the OTP request using Burp Suite.
Forward the Request: I forward the request through Burp Suite until I see the OTP and mobile number details.
Modify the Intercept Settings: I then right-click on the intercepted request and select ‘Do Intercept > Response to this Request’ to start intercepting the response.
Error Response Code: As I forward the request, a ‘400 Bad Request’ response page will appear.
Submit the Modified Request: At this point, I change the response code to ‘200 OK’ and use the previously captured successful access token. After modifying the response, I submit the request. I successfully gain access to the account without needing a valid OTP.
Verification: To verify the login, I add a product to my cart, proceed to the place order page, and see that my mobile number is automatically filled in, as my login was successful.
Implications and Recommendations
This vulnerability poses a significant risk as it allows unauthorized access to user accounts, potentially leading to data breaches and unauthorized transactions. Any organization must address this vulnerability promptly to protect their users.
Recommendations:
- Implement Stronger Validation: Ensure that the OTP verification mechanism includes robust validation checks.
- Use Secure Communication: Implement secure communication channels, such as HTTPS, to protect data in transit.
- Regular Security Audits: Conduct regular security audits and penetration testing to identify and address potential vulnerabilities.
Conclusion
The discovery of the OTP bypass vulnerability in this website login process underscores the importance of rigorous security measures in protecting user data. Companies must continually evaluate and strengthen their security protocols to prevent unauthorized access and protect their users’ privacy.
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