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GHSA-rch3-82jr-f9w9

Jupyter Notebook Vulnerable to Authentication Token Theft via CommandLinker XSS

Source: GitHub Advisory Database (reviewed) High CVE-2026-40171

Packages

EcosystemPackageAffectedFixed in
npm @jupyter-notebook/help-extension >= 7.0.0, < 7.5.6 7.5.6
PyPI notebook >= 7.0.0, < 7.5.6 7.5.6
PyPI jupyterlab < 4.5.7 4.5.7
npm @jupyterlab/help-extension < 4.5.7 4.5.7

Details

As written in the advisory (Markdown source, shown as plain text).

### Impact A stored Cross-Site Scripting (XSS) vulnerability in Jupyter Notebook allows attackers to steal authentication tokens from users who open malicious notebook files and interact with elements that the attacker can make look indistinguishable from legitimate controls (single click interaction). The vulnerability enables complete account takeover through the Jupyter REST API, allowing the attacker to: 1. Read all files 2. Modify/create files 3. Access running kernels and execute arbitrary code 4. Create terminals for shell access ### Patches Jupyter Notebook 7.5.6 and JupyterLab 4.5.7 include patches for this vulnerability. ### Workarounds The help extension can be disabled via CLI: ``` jupyter labextension disable @jupyter-notebook/help-extension jupyter labextension disable @jupyterlab/help-extension ``` ### Hardening The patched versions include a toggle to disable the command linker functionality altogether, for example via `overrides.json`: ```json { "@jupyterlab/apputils-extension:sanitizer": { "allowCommandLinker": false } } ``` ### Resources - https://jupyterlab.readthedocs.io/en/latest/user/commands.html#commands-in-markdown-output-and-files ### Acknowledgments Reported by Daniel Teixeira - NVIDIA AI Red Team

References

External links from the advisory. They lead to third-party sites.