A CSS selector is a pattern that browser code uses to find one or more elements on a web page, such as a button, form field, or menu item. Developers often build selectors from known values to update the interface, attach events, or trigger actions in admin pages and other dynamic apps.
In security, selectors matter because unsafe user input can change what the browser matches. If an attacker can inject part of a selector, the page may target the wrong element, hide warnings, or simulate a click on a sensitive control. That can turn a harmless preview or UI update into an unintended action, especially in privileged dashboards. Defenses include escaping untrusted values, avoiding selector construction from raw input, and validating that the code targets only the intended elements.