WordPress 6.9 — 6.9.1 - Missing Authorization to Authenticated (Subscriber+) Arbitrary Note Creation via REST API

WordPress core is vulnerable to unauthorized access in versions 6.9 through 6.9.1. The Notes feature (block-level collaboration annotations) was introduced in WordPress 6.9 to allow editorial comments directly on posts in the block editor.

However, the REST API create_item_permissions_check() method in the comments controller did not verify that the authenticated user has edit_post permission on the target post when creating a note. This makes it possible for authenticated attackers with Subscriber-level access to create notes on any post, including posts authored by other users, private posts, and posts in any status.