Update the plugin.
An unknown person discovered and reported this Cross Site Scripting (XSS) vulnerability in WordPress All In One WP Security & Firewall 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 4.2.2.
Multiple CrossSite Request Forgery (CSRF) vulnerabilities
Authenticated Arbitrary Redirect / Reflected XSS vulnerability
Authenticated CrossSite Scripting (XSS) vulnerability
Reflected CrossSite Scripting (XSS) vulnerability