CAPEC Definitions

    CAPEC Definitions / CAPEC-592

    CAPEC-592: Stored XSS

    An adversary utilizes a form of Cross-site Scripting (XSS) where a malicious script is persistently stored within the data storage of a vulnerable web application as valid input.

    Severity:Very High
    Possibility:High

    Extended Description

    Initially presented by an adversary to the vulnerable web application, the malicious script is incorrectly considered valid input and is not properly encoded by the web application. A victim is then convinced to use the web application in a way that creates a response that includes the malicious script. This response is subsequently sent to the victim and the malicious script is executed by the victim's browser. To launch a successful Stored XSS attack, an adversary looks for places where stored input data is used in the generation of a response. This often involves elements that are not expected to host scripts such as image tags (<img>), or the addition of event attributes such as onload and onmouseover. These elements are often not subject to the same input validation, output encoding, and other content filtering and checking routines.

    Mitigations

    Use browser technologies that do not allow client-side scripting.

    Utilize strict type, character, and encoding enforcement.

    Ensure that all user-supplied input is validated before being stored.

    Relationships with other CAPECs

    CAPEC-63: Cross-Site Scripting (XSS)

    Prerequisites

    An application that leverages a client-side web browser with scripting enabled.

    An application that fails to adequately sanitize or encode untrusted input.

    An application that stores information provided by the user in data storage of some kind.

    Related Weaknesses

    CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')