User Access Manager <= 2.3.12 - Authenticated (Subscriber+) SQL Injection

Summary

The User Access Manager plugin for WordPress is vulnerable to Second-Order SQL Injection via the 'id' parameter of the wp_ajax_save-attachment-compat AJAX action in versions up to, and including, 2.3.12. This is due to insufficient validation on the objectId value stored in the saveAjaxAttachmentData() function and subsequent unparameterized concatenation in the addQueryExcludedPostFilter() function — the stored value is later retrieved from the database and used as an array key, then directly imploded into a SQL NOT IN() clause without integer casting or prepared statements. This makes it possible for authenticated attackers, with subscriber-level access and above, to append additional SQL queries into already existing queries that can be used to extract sensitive information from the database.