The user is the individual or organization that uses the product or service and bears the risk of a vulnerability; users receive advisories and remediations and act on them, and can also be reporters; the vendor's disclosure process exists to reduce users' risk by giving them the information and remediation they need to identify and fix vulnerable systems (the advisory definition of 3.8).
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.