Grav versions 2.0.0-rc.9 and the current 2.0 branch contain a stored CSS injection vulnerability via the Markdown image resize() media action. This allows a lower-privileged content editor to inject arbitrary CSS declarations into the style attribute of rendered images, which are then executed in the context of higher-privileged users viewing the content. The vulnerability arises because the resize() method does not properly sanitize or validate input values before embedding them as CSS style attributes. This can lead to UI redress attacks such as overlays that manipulate the admin interface. A patch is available to properly sanitize these inputs.