MISP Stored Cross-Site Scripting (XSS) via Unvalidated Event Graph Preview Image

MISP contains a stored cross-site script (XSS) vulnerability in the event graph preview feature.

The event graph preview image field was accepted and stored without server-side validation. On the client side, the stored value was rendered into an HTML img element's src attribute via string concatenation, allowing a crafted value to break out of the attribute context and inject arbitrary script.

Preconditions:

- An authenticated MISP user with the ability to create or modify an event graph entry.

- A second user (the victim) who views the event graph and triggers the preview popover.

Impact:

- Execution of arbitrary JavaScript in the victim's browser within the MISP application context.

- Potential theft of session tokens, cookies, or sensitive data accessible to the victim's browser.

- Potential for performing actions on behalf of the victim within the MISP application.

Affected: MISP versions prior to the fix (commit applied after v2.5.48).