Oxygen Builder < 4.8.3 - Authenticated (Contributor+) Remote Code Execution

Description

The Oxygen Builder plugin for WordPress is vulnerable to Remote Code Execution in all versions up to, and including, 4.8.2 via post metadata. This is due to the plugin storing custom data in post metadata without an underscore prefix. This makes it possible for lower privileged users, such as contributors, to inject arbitrary PHP code via the WordPress user interface and gain elevated privileges.