A validation issue allowed some functionality, such as Webmentions, to be abused by an unauthenticated user to make limited HTTP requests to hosts in the Ghost server's internal network. A successful attack would not result in any response data being returned.

This vulnerability is present in Ghost from v6.26.0 up to v6.54.0.

v6.54.1 contains a fix for this issue.

For self-hosters using Docker, find [Docker's official Ghost image here](https://hub.docker.com/ /ghost). Updating a Docker-based Ghost instance is documented here.

If your Ghost is a Ghost-CLI install see our documentation on updating it to the latest version here.

Ghost thanks Hwang Seyeon for disclosing this vulnerability responsibly.

If you have any questions or comments about this advisory, email Ghost at security@ghost.org.