SSO + CRSF causes 403 errors

We are running jenkins behind an apache proxy

Since the latest update, the kerberos sso plugin will cause issues related to the CSRF security policy that is enabled by default.

If we only disable the Kerberos SSO, and log in manually using LDAP credentials, everything works as expected.

If we only disable the CSRF Protection, and login using SSO, everything works as expected

(besides a remote API call, that requires CSRF to be enabled)

But when both CSRF and SSO are enabled, the automatic login works perfectly.

But the moment you try to do a form submit, like starting a job, we will get a 403 - Forbidden error.

This has been working perfectly for a few years. So a recent update broke this.

Perhaps the SSO plugin needs an update, related to another recent change in how CSRF is handled ?