Update the plugin.
An unknown person discovered and reported this Cross Site Scripting (XSS) vulnerability in WordPress WP Super Cache Plugin. This could allow a malicious actor to inject malicious scripts, such as redirects, advertisements, and other HTML payloads into your website which will be executed when guests visit your site. This vulnerability has been fixed in version 1.4.5.
Cache Poisoning vulnerability
Authenticated Persistent CrossSite Scripting (XSS) vulnerability
Authenticated Remote Code Execution (RCE) vulnerability
PHP Object Injection