The Shortcodes Ultimate plugin for WordPress, also known as WP Shortcodes, has a security flaw that allows attackers to insert harmful code into web pages. This can be done by using certain shortcodes in the plugin, and it affects all versions up to 7.1.2. The issue is caused by the plugin not properly filtering and protecting user-inputted attributes. As a result, users with contributor-level or higher access can potentially run malicious scripts on any page that contains the harmful shortcode.