Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
The Yuzo Related Posts plugin 5.12.94 for WordPress has XSS because it mistakenly expects that is_admin() verifies that the request comes from an admin user (it actually only verifies that the request is for an admin page). An unauthenticated attacker can inject a payload into the plugin settings, such as the yuzo_related_post_css_and_style setting.
CWE-79 - Cross Site Scripting
Cross-Site Scripting, commonly referred to as XSS, is the most dominant class of vulnerabilities. It allows an attacker to inject malicious code into a pregnable web application and victimize its users. The exploitation of such a weakness can cause severe issues such as account takeover, and sensitive data exfiltration. Because of the prevalence of XSS vulnerabilities and their high rate of exploitation, it has remained in the OWASP top 10 vulnerabilities for years.