From the ISC2 website: Beginning in April 2018, the CISSP® exam will be based on a new exam outline. In advance of the new exam outline being available, the Detailed Content Outline (DCO) is currently available. The DCO is a less detailed version of the exam outline but will give you an overview.
I have asked this question on the ISC2 community website. See the response I have received within this article. I have reformatted the article for the look but it is the verbatim response that I have received from ISC2.