By default, the WordPress administrator and editor roles can add unfiltered HTML content in various places, such as post content. This includes the
capability to add JavaScript code.
If an account with such a role gets hijacked, this capability can be used to plant malicious JavaScript code that gets executed whenever somebody
visits the website.
This may lead to Cross-Site Scripting (XSS) attacks, which can be used to steal other users' credentials or perform actions on behalf of other
users.