👋 Hey Everyone!

I'm Ch4ndan Das First of all, thank you very much for the support on my previous articles. I am genuinely trying to share my bug hunting experiences to help others — especially beginners. Please ignore any small mistakes and focus on the value.

Lets start !

I selected a target on Bugcrowd — let's call it target.com — and started testing the registration functionality. If you also want to find this type of bug, you first need to understand the application's logic.

Summary:

The mobile application does not properly validate the OTP (One-Time Password) during the registration or login process. An attacker can bypass the OTP verification step and gain unauthorized access to an account without entering a valid OTP.

Steps to Reproduce

  1. Go to https://target.com/en/home
  2. Enter a mobile number and request the OTP.
  3. Enter an incorrect OTP.
  4. Capture the request using Burp Suite.
  5. Change "method":"verify" to "method":"login" in the request.
None
1st Response (Original)
None
Modified Response

6. Send the request and observe that the OTP verification is bypassed.

None
Bugcrowd Response