@Override
    public boolean validateIssuer(final WebContext webContext, final List<String> endpoints,
                                  final OidcRegisteredService registeredService) {
        val requestUrl = webContext.getRequestURL();
        val definedIssuer = determineIssuer(Optional.ofNullable(registeredService));
        val definedIssuerWithSlash = StringUtils.appendIfMissing(definedIssuer, "/");
        
        val foundMatch = endpoints.stream().anyMatch(endpoint -> {
            val issuerFromRequestUrl = StringUtils.removeEnd(StringUtils.remove(requestUrl, '/' + endpoint), "/");
            return definedIssuer.equalsIgnoreCase(issuerFromRequestUrl)
                || issuerFromRequestUrl.startsWith(definedIssuerWithSlash)
                || definedIssuer.startsWith(issuerFromRequestUrl)
                || RegexUtils.find(properties.getCore().getAcceptedIssuersPattern(), issuerFromRequestUrl);
        });
        if (!foundMatch) {
            LOGGER.debug("Cannot accept issuer [{}] at [{}] for any of the endpoints [{}]",
                webContext.getRequestURL(), endpoints, definedIssuer);
        }
        return foundMatch;
    }
This is {@link OidcDefaultIssuerService}.

@author Misagh Moayyed
@since 6.4.0
support/cas-server-support-oidc-core-api/src/main/java/org/apereo/cas/oidc/issuer/OidcDefaultIssuerService.java