protected static boolean isLogoutRequestConfirmed(final RequestContext requestContext) {
        val request = WebUtils.getHttpServletRequestFromExternalWebflowContext(requestContext);
        return request.getParameterMap().containsKey(REQUEST_PARAM_LOGOUT_REQUEST_CONFIRMED);
    }
Parameter to indicate logout request is confirmed.
support/cas-server-support-actions-core/src/main/java/org/apereo/cas/web/flow/logout/TerminateSessionAction.java