Input validation vulnerability in iThemes Security 5.3.5

The iThemes Security plugin for WordPress is vulnerable to a type of attack called Cross-Site Scripting (XSS). Versions up to and including 5.3.4 of the plugin have a security flaw that does not properly filter data input or protect the code from malicious attacks. An attacker who is authenticated can inject a malicious script into a page, which will be executed whenever someone visits that page.