Full Account Takeover at One of the Largest E-Commerce Companies

bug bounty

Introduction

During my journey as a bug bounty hunter, I recently identified a severe vulnerability leading to a full account takeover at one of the largest e-commerce companies. This write-up details the technical steps I followed, the impact of the vulnerability, and the eventual resolution.

The Vulnerability

The issue was found in the password reset functionality, specifically involving password reset link poisoning. The application's logic failed to verify critical parameters, allowing attackers to manipulate the reset process.

How It Worked:

  1. Password Reset Request:
    • A user initiates a password reset, and the application sends an email with a reset link.
  2. Exploitation:
    • The attacker intercepts the reset link and modifies certain parameters.
    • This allowed unauthorized access to another user's account without their knowledge.

Key Flaw:

The lack of proper validation on the server-side enabled this attack. Once the poisoned link was accessed, the victim’s account could be controlled completely.

Technical Details

  1. Vulnerable Endpoint:

    https://ecommerce.com/reset-password?token=<JWT>&user_id=<USER_ID>

  2. Exploitation Steps:

    • The attacker generated a legitimate reset link for their account.
    • They replaced the user_id with the target user’s ID while keeping their valid token.
    • Upon visiting the link, the system incorrectly associated the reset with the victim's account.

  3. Result:

    • The attacker could set a new password for the victim’s account, achieving full account takeover.

Impact

This vulnerability exposed millions of user accounts to potential compromise. With access to an account, an attacker could:

  • View personal details such as addresses and order history.
  • Make unauthorized purchases.
  • Exploit saved payment methods.

Resolution

I reported this vulnerability through the company’s bug bounty program. After triage, the issue was fixed by implementing strict validation checks:

  • Linking reset tokens with specific users in the database.
  • Rejecting any mismatch between token and user_id.

The company awarded me a generous bounty and publicly acknowledged my contribution.

Lessons Learned

  1. Secure All Entry Points:

    • Password reset functionalities are high-value targets and must be designed with utmost care.

  2. Validate Everything:

    • Always validate user-provided inputs on the server-side to prevent tampering.

  3. Bug Bounty Impact:

    • Reporting such issues strengthens platforms and secures users worldwide.

Conclusion

Discovering this vulnerability reinforced the importance of attention to detail and secure coding practices. I am proud to have contributed to securing such a major platform.

Feel free to reach out or follow me for more insights into the world of cybersecurity!

Author: m0uka

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