GHSA-gfjp-2p8f-94qv: XSS
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 security@ghost.org.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/ghostto a version that resolves this vulnerability.Fixed in 6.64.0 - Upgrade
Upgrade
Ghostto a version that resolves this vulnerability.Fixed in 6.64.0
Event History
Frequently Asked Questions
Which deployments are affected?
Affected deployments are Ghost versions 6.22.1 through 6.64.0 that use the default local storage adapter. The issue concerns uploaded files being served with a content type derived from their file extension.
What access does an attacker need?
An attacker needs staff-user access that allows them to upload files. Exploitation also requires another staff user to interact with attacker-hosted script content, potentially allowing compromise of that user's admin session.
Is there a fix available?
Yes. Ghost v6.64.0 contains the fix. Self-hosted Docker and Ghost-CLI installations should be updated using their applicable Ghost update process.