The Invoice123 plugin for WordPress is vulnerable to authorization bypass in all versions up to, and including, 1.7.0. This is due to the plugin not properly verifying that a user is authorized to perform an action. This makes it possible for authenticated attackers, with subscriber-level access and above, to overwrite the plugin's API key stored in wp_options, modify invoice plugin settings, and alter WooCommerce tax rate data in the wp_woocommerce_tax_rates table.