Ghost: Stored XSS via File Uploads on Local Storage

Impact

Ghost restricts the content type that uploaded files are served with, to prevent browsers from executing them. On sites using the default local storage adapter, this restriction was not applied, so files uploaded by any staff user were served with a content type derived from their file extension. This could be used to host scripts on the site's domain, possibly resulting in compromise of other staff users' admin sessions.

Vulnerable versions

This vulnerability is present in Ghost from v6.22.1 up to v6.64.0.

Patches

v6.64.0 contains a fix for this issue.

How to update

For self-hosters using Docker, find Docker's official Ghost image here. 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.

References

Ghost thanks evertrustai, Thai Son Dinh of VinSOC Labs, Enis Atılgan, Doan Manh Duc, Harshit Gupta (Mr HAX), 白墨, and Mukul of Parameter for disclosing this vulnerability responsibly.

For more information

If you have any questions or comments about this advisory, email us at [email protected].