Origin: null on SAML POST

Getting advice
1

We use Keycloak for SAML IDP Initiated access to different SSO’s. One SSO is getting a CORS error because the Origin in the POST request is null. Can the Origin for SAML in Keycloak be set somewhere? The documentation shows where you set web origin for OpenID but not for SAML. Below is an example of the issue.

POST Protected Page SAML Demo Service Provider HTTP/1.1
sec-ch-ua: “Chromium”;v=“130”, “Google Chrome”;v=“130”, “Not?A_Brand”;v=“99”
sec-ch-ua-mobile: ?0
sec-ch-ua-platform: “Windows”
Origin: null
Content-Type: application/x-www-form-urlencoded
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/130.0.0.0 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,/;q=0.8,application/signed-exchange;v=b3;q=0.7
Sec-Fetch-Site: cross-site
Sec-Fetch-Mode: navigate
Sec-Fetch-Dest: document
Accept-Encoding: gzip, deflate, br, zstd
Accept-Language: en-US,en;q=0.9

2

I tried going straight to keycloak to see if my application was causing an issue, but I still see Origin: null in the header.

My realm is named SamlTest and client is named sso. When I go to the URL below it asks me to login and then redirects me to the sso, but since the header doesn’t have the Origin set it fails.
https:/mykeycloak.com:8443/realms/SamlTest/protocol/saml/clients/sso

Can Keycloak not set the Origin header when it does a POST SAML requests to a URL?