MISP: Stored XSS via Inline-Served SVG Organisation Logos and Report Pictures

Affected versions of MISP serve uploaded SVG images inline without a restrictive browser sandbox.

The commit explains that SVG files are XML documents rather than passive bitmap images. While scripts inside SVG do not execute when the SVG is rendered through a normal <img>, they can execute when the SVG is navigated to directly or embedded as a document. In that case, malicious <script> elements, event handlers, or javascript: URLs execute on the MISP origin with the viewer’s session.

The affected use cases include:

 - organisation SVG logos;
 - event-report SVG pictures.

Importantly, the vulnerable behavior is on the serve path, not merely the upload path: the patch notes that a malicious SVG uploaded while SVG support was enabled could remain dangerous even after uploads were later disabled.

Version affected: ≤2.5.45