The vulnerability in Grav CMS 2.0.10 arises from improper limitation of a pathname in the ImageMedium::watermark() method. The method passes an unsanitized $image argument to RocketTheme\Toolbox\ResourceLocator\UniformResourceLocator::findResource(). The file:// scheme branch only lexically collapses '..' segments without performing a realpath or containment check. This allows an attacker who can author Markdown image syntax to include traversal sequences that cause arbitrary image files outside Grav's media sandbox to be composited into a carrier image. This composite image is then cached and served publicly without authentication, leading to unauthorized disclosure of files.

An unauthenticated attacker can cause Grav CMS to disclose arbitrary image files outside the intended media sandbox by exploiting the path traversal vulnerability. These files are composited into a carrier image, cached, and served from a public URL accessible to anonymous visitors. This results in unauthorized information disclosure of potentially sensitive files.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. No official fix or temporary workaround is provided in the available data. Until a patch is available, restrict Markdown image syntax editing to trusted users and monitor for suspicious usage if possible.