The WP Shortcodes Plugin, also known as Shortcodes Ultimate, is a plugin for WordPress that allows users to easily add special features to their website. However, it has a security vulnerability that can allow hackers to insert harmful code into web pages. This can happen when someone with contributor-level access or higher uses a specific feature called su_dailymotion. This feature does not properly check and protect against malicious code, making it possible for attackers to execute their own code when someone visits the affected page.