This post is regarding one of my findings in Facebook, which could have allowed anyone to bypass Multi-factor authentication.
Vulnerability Type :
Two-factor authentication is a security mechanism that requires two types of credentials for authentication and is designed to provide an additional layer of validation, minimizing security breaches.
Two-factor authentication can be bypassed using the add instagram account feature in facebook business . While merging the victim account with the attacker facebook account, 2FA of victim account gets automatically bypassed which an attacker use 2fa enabled victim account without entering 2FA process.
Proof of Concept
1) User “A” creates a business account and Adds victim Two-factor authentication enabled account.
2) add victim username and password (2FA enabled account)
3) here you can see 2FA check skipped when a Business Manager tries to link an Instagram Account
I would like to thanks Facebook Security Team for this awesome Response .
Have a great day ahead ☺