Keycloak: Unauthorized account takeover via WebAuthn token replay

A flaw was found in Keycloak. This authentication vulnerability allows a remote attacker to replay ExecuteActionsActionToken tokens within Keycloak's WebAuthn (Web Authentication) flow. By intercepting an execute-actions email link, an attacker can register their own authenticator to a victim's account. This leads to unauthorized enrollment of a hardware-backed credential, enabling persistent account takeover.