The Gutenberg Template Library & Redux Framework plugin <= 4.2.11 for WordPress used an incorrect authorization check in the REST API endpoints registered under the “redux/v1/templates/” REST Route in “redux-templates/classes/class-api.php”. The `permissions_callback` used in this file only checked for the `edit_posts` capability which is granted to lower-privileged users such as contributors, allowing such users to install arbitrary plugins from the WordPress repository and edit arbitrary posts.

The Gutenberg Template Library & Redux Framework plugin <= 4.2.11 for WordPress registered several AJAX actions available to unauthenticated users in the `includes` function in `redux-core/class-redux-core.php` that were unique to a given site but deterministic and predictable given that they were based on an md5 hash of the site URL with a known salt value of '-redux' and an md5 hash of the previous hash with a known salt value of '-support'. These AJAX actions could be used to retrieve a list of active plugins and their versions, the site's PHP version, and an unsalted md5 hash of site’s `AUTH_KEY` concatenated with the `SECURE_AUTH_KEY`.