GHSA-fcr8-4r9f-r66m
nbgrader's `frame-ancestors: self` grants all users access to formgrader
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
nbgraderReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Impact
Enabling frame-ancestors: 'self' grants any JupyterHub user the ability to extract formgrader content by sending malicious links to users with access to formgrader, at least when using the default JupyterHub configuration of enable_subdomains = False.
#1915 disables a protection which would allow user Alice to craft a page embedding formgrader in an IFrame. If Bob visits that page, his credentials will be sent and the formgrader page loaded. Because Alice's page is on the same Origin as the formgrader iframe, Javasript on Alice's page has full access to the contents of the page served by formgrader using Bob's credentials.
Workarounds
- Disable
frame-ancestors: self, or - enable per-user and per-service subdomains with
JupyterHub.enable_subdomains = True(then even if embedding in an IFrame is allowed, the host page does not have access to the contents of the frame).
References
JupyterHub documentation on why and when frame-ancestors: self is insecure, and why it was disabled by default: https://jupyterhub.readthedocs.io/en/stable/explanation/websecurity.html#:~:text=frame-ancestors
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | nbgrader | ≥ 0.9.4&&< 0.9.5 | 0.9.5 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nbgrader. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update nbgrader to 0.9.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fcr8-4r9f-r66m is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-fcr8-4r9f-r66m is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-fcr8-4r9f-r66m. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-fcr8-4r9f-r66m in your dependencies?
O3 detects GHSA-fcr8-4r9f-r66m across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.