Grav is an open-source, flat-file content management system. A file upload path traversal vulnerability has been identified in the application prior to version 1.7.45, enabling attackers to replace or create files with extensions like .json, .zip, .css, .gif, etc. This critical security flaw poses severe risks, that can allow attackers to inject arbitrary code on the server, undermine integrity of backup files by overwriting existing files or creating new ones, and exfiltrate sensitive data using CSS exfiltration techniques.

Upgrading to patched version 1.7.45 can mitigate the issue.