The Post Grid Gutenberg Blocks and WordPress Blog Plugin – PostX plugin for WordPress is vulnerable to unauthorized plugin installation/activation due to a missing capability check on the 'install_required_plugin_callback' function in all versions up to, and including, 4.1.16. This makes it possible for authenticated attackers, with Subscriber-level access and above, to install and activate arbitrary plugins which can be leveraged to achieve remote code execution if another vulnerable plugin is installed and activated.