Theme Preview is a WordPress feature that lets an authenticated user see how a theme will look before it is activated. It is meant to be a safe, visual step in theme management, separate from installing or enabling code on the site.
In security terms, theme preview matters because it sits near a trust boundary: the request comes from a logged-in session, but it still has to be parsed and handled safely. If preview URLs are interpreted inconsistently, an attacker can abuse that gap to steer the administrator into unwanted actions, such as loading attacker-controlled content or triggering hidden install logic. Defenders should treat preview flows as security-sensitive, enforce capability checks and nonce validation, and review any custom code that touches preview, AJAX, or theme-install paths. A preview should display a theme, not become a path to server-side code execution.