Stored or persistent cross-site scripting (XSS) is a type of XSS where the attacker first sends the payload to the web application, then the application saves the payload (e.g., in a database or server-side text files), and finally, the application unintentionally executes the payload for every victim visiting its web pages.
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.