2F-Authentication Bypass in Sign-up Page

Hello everyone, Today i’m going to share how i found 2F-Authentication Bypass vulnerability in singup page and found the same vulnerability in 4 other domains.

Bug-type: 2F-Authentication
website: example.com

Let’s start

I was able to register the account on behalf of any person by just having there mobile number and email(optional).

Because 2F-Authentication OTP is reflecting in response tab, when you intercept the request easily you can copy the OTP and paste it .

Steps to reproduce
1) Go to https://example.com/register and input a victim username, email-id and mobilenumber
2) Click on send OTP and intercept the request (Burpsuite)
3) In responce tab you can the see the mobile number and OTP
4) By using the OTP you can easily register to the account.

Impact
1) Full account takeover of the victim.
2) The attacker can do whatever he want in the name of victim by using his email-id and mobile number.

Tips
1) Always keep running the Burp-Suite in background.
2) Don’t give up.