Cors error with post /logout with _csrf token while triggering Single Llogout in IDP

Question

I am using SimpleSamlPHP 2.x as an Identity Provider (IDP) along with Spring Boot 2.7. My Spring SAML Security (spring-security-saml2-service-provider) version is 5.7.5 (recently updated).

Currently, I can perform SAML Single Logout (SLO) without any issues using the GET /logout request. However, this triggers a confirmation dialog in Spring Security, asking "Do you want to logout?" I'd like to bypass this dialog and perform a direct logout.

To achieve this, I tried using a form-based POST /logout from my Angular frontend app. I included the XSRF token in the header and _csrf in the payload. The process successfully triggers SLO and returns a 302 status code, which then redirects to the IDP. The SAMLRequest in the redirect URL looks like this: https://my-idp:8443/sso/module.php/saml/idp/singleLogout?SAMLRequest=***.

However, the browser displays a CORS error:

The error, "(redirected from 'http://localhost:8000/service-provider/logout')", originating from 'http://localhost:8000', is blocked by the CORS policy. The preflight request's access control check failed, as there is no 'Access-Control-Allow-Origin' header on the requested resource.

My post request from my FE angular is as

`logMeOut(){
    const csrfToken = this.getCookie('XSRF-TOKEN');
    const formData = new FormData();
    formData.append('_csrf', csrfToken);
    
const headers = new HttpHeaders({
        'Content-Type': 'application/x-www-form-urlencoded',
        'XSRF-TOKEN': csrfToken,
    });

    const options = {
        headers,
        withCredentials: true, // Include cookies in the request
    };
    this.http.post(‘/service-provider/logout', formData, options).subscribe(() => {
        console.log("Logout Success ")
    });
}`