Input validation vulnerability in Yoast SEO 21.0

The Yoast SEO plugin for WordPress, up to and including version 21.0, is not secure. It has a problem with how it handles incoming and outgoing data, which means that someone who has access to the plugin with the correct permissions could add malicious code to a webpage. If a user visits a page with the malicious code, the code will run, potentially causing harm to the user’s computer.