Lab: 2FA broken logic
Summary: PortSwigger's Web Security Academy lab describes a two-factor authentication flaw in which the POST /login2 request uses a verify parameter to determine which user's account is being accessed. The solution changes verify to carlos to generate a temporary 2FA code for the victim, then brute-forces the mfa-code parameter in Burp Intruder until a 302 response grants access to Carlos's account page.
Bottom line: The account being protected here is chosen by a client-supplied parameter, so an attacker who can name the victim can trigger a code for that victim and guess it without ever knowing their password.
Read the original at PortSwigger Research ↗
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