protected boolean isClientSecretUndefined(final OAuthRegisteredService registeredService) {
        return registeredService != null && StringUtils.isBlank(registeredService.getClientSecret());
    }
This is {@link DefaultOAuth20ClientSecretValidator}.

@author Misagh Moayyed
@since 6.6.0
support/cas-server-support-oauth-core-api/src/main/java/org/apereo/cas/support/oauth/validator/DefaultOAuth20ClientSecretValidator.java