It means that any bug which lets an attacker get privileged access is now a potentially hard to recover compromise below the operating system kernel, but Secure

It means that any bug which lets an attacker get privileged access is now a potentially hard to recover compromise below the operating system kernel, but Secure Boot still passes. That means a compromise might no longer be recoverable short of trashing the hardware, and it could be triggered in many ways from some kind of exploit to having a few minutes alone with the hardware to tricking someone into running an installer.