The Comments WordPress plugin before 7.6.66 does not validate a value used to build a database query, allowing unauthenticated users to inject SQL and read comments they are not entitled to see, including comments awaiting moderation, comments marked as spam or trashed, and comments on private and draft posts.
The injected text reaches the query as grammar rather than as data and does not yield extraction of arbitrary data, so the confidentiality impact is the disclosed comment content rather than the database at large.