WebAuthn4J Spring Security provides Web Authentication specification support for Spring applications. Affected versions are subject to improper signature counter value handling. A flaw was found in webauthn4j-spring-security-core. When an authenticator returns an incremented signature counter value during authentication, webauthn4j-spring-security-core does not properly persist the value, which means cloned authenticator detection does not work. An attacker who cloned valid authenticator in some way can use the cloned authenticator without being detected.