MISP contains a cross-site scripting (XSS) vulnerability in the remote event preview page. When a linked (remote) MISP server is configured, the event preview renders tag identifiers inside an inline JavaScript onclick attribute. The tag ID value was HTML-escaped but not sanitized for the JavaScript string context, meaning a malicious linked server could supply a tag ID containing characters (such as a single quote) that break out of the JavaScript string literal and inject arbitrary script.

Preconditions:

- A linked/remote MISP server is configured and connected to the local instance.

- The linked server supplies a crafted tag ID in an event.

- An authenticated user views the event preview and interacts with the affected tag element.

Impact:

- Arbitrary JavaScript execution in the context of the viewing user's browser session, potentially allowing session hijacking, data exfiltration, or unauthorized actions on behalf of the user.

Affected versions: MISP prior to the fix commit (v2.5.48 or later, exact boundary unconfirmed).