Taxonomy filter <= 2.2.9 - Cross-Site Request Forgery via taxonomy_filter_save_main_settings()

The Taxonomy filter plugin for WordPress is vulnerable to Cross-Site Request Forgery in versions up to, and including, 2.2.9. This is due to missing or incorrect nonce validation on the taxonomy_filter_save_main_settings() function. This makes it possible for unauthenticated attackers to update the plugin's settings via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.