Jupyter Notebook Vulnerable to Authentication Token Theft via CommandLinker XSS

### 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

Source published

30 Apr 2026 17:25:47 UTC

Source modified

10 Sep 2026 03:51:03 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Publisher rating · HIGH