I've built idp.war 2.4.4_sp4 with update which pass relyingPartyId from IDP to oxAuth in authorization request.
Now yo can get in script origin_headers from session. Here is example:
```
{"scope":"openid profile email user_name","response_type":"code id_token","origin_headers":"https://sp.gluu.org/shibboleth","nonce":"nonce","redirect_uri":"https://nest.gluu.org/idp/auth-code.jsp","remote_ip":"192.168.15.1","auth_step":"1","client_id":"@!6BED.0CBA.D569.AA67!0001!6E3D.B9BF!0008!082F.319E","acr":"internal"}
```
Here is code in the script code to get it:
```
context = Contexts.getEventContext()
session_attributes = context.get("sessionAttributes")
if session_attributes.containsKey("origin_headers):
origin_headers = session_attributes.get("origin_headers")
```