Flexible Checkout Fields for WooCommerce <= 2.3.1 - Unauthenticated Arbitrary Plugin Settings Update

The Flexible Checkout Fields for WooCommerce plugin for WordPress is vulnerable to Unauthenticated Arbitrary Plugin Settings update, in addition to Stored Cross-Site Scripting in versions up to, and including, 2.3.1. This is due to missing authorization checks on the updateSettingsAction function...