Executive brief
The Royal MCP plugin for WordPress, which provides integration tools for Model Context Protocol (MCP), contains a security flaw that fails to verify user permissions for many of its core functions. This allows any registered user on the site, even those with the lowest level of access like a Subscriber, to read private content, view a list of all users and their roles, and create or delete posts. This could lead to unauthorized data exposure and significant disruption of website content.
Technical details
The Royal MCP plugin for WordPress (versions prior to 1.4.26) suffers from an insufficient authorization vulnerability (CWE-862). While the plugin implements token-based authentication (OAuth 2.1 + PKCE), it fails to perform subsequent WordPress capability checks on the majority of its MCP tool endpoints after a session is initialized. An attacker with a low-privileged account (such as a Subscriber) can authenticate via the MCP flow and then invoke JSON-RPC methods like 'wp_create_post', 'wp_update_post', 'wp_get_users', and 'wp_delete_post'. This allows for full CRUD operations on posts and user enumeration, bypassing intended role-based access controls. The issue is fixed in version 1.4.26.
Affected products
- Royal MCP Royal MCP < 1.4.26
Timeline
- 2026-06-10: disclosed: Initial public disclosure by WPScan
- 2026-06-10: patched: Fix released in version 1.4.26
- 2026-07-01: advisory: CVE-2026-10750 published to NVD