MFA challenge interception is an attack technique where an adversary relays, proxies, or captures the extra verification step used to finish a login. Instead of stealing only a password, the attacker tricks the victim into approving a push notification, entering a one-time code, or responding to a fake authentication page. The attacker then uses that challenge response to complete the session.
This matters because multi-factor authentication is often treated as a final barrier, but some MFA methods are still phishable. In real attacks, it appears in man-in-the-middle phishing kits, adversary-in-the-middle proxies, and fake login portals that mirror legitimate services. Defenders reduce this risk with phishing-resistant MFA such as passkeys or hardware security keys, session binding, and alerts for unusual login prompts or repeated challenge attempts.