phpMyFAQ before 4.1.7 fails to persist the WebAuthn login challenge generated by prepareForLogin, because neither WebAuthn controller saves the mutated key objects back to the database. At login the …

Summary

phpMyFAQ before 4.1.7 fails to persist the WebAuthn login challenge generated by prepareForLogin, because neither WebAuthn controller saves the mutated key objects back to the database. At login the anti-replay comparison is skipped by its own null guard, allowing an attacker who captures a successful WebAuthn assertion to replay it indefinitely and authenticate as the user without any interaction or hardware key.