PYSEC-2026-1481

Impact

The vulnerability depends on user interaction by opening a malicious notebook with Markdown cells, or Markdown file using JupyterLab preview feature.

A malicious user can access any data that the attacked user has access to as well as perform arbitrary requests acting as the attacked user.

Patches

JupyterLab v3.6.8, v4.2.5 and Jupyter Notebook v7.2.2 were patched.

Workarounds

There is no workaround for the underlying DOM Clobbering susceptibility. However, select plugins can be disabled on deployments which cannot update in a timely fashion to minimise the risk. These are:

• @jupyterlab/mathjax-extension:plugin - users will loose ability to preview mathematical equations
• @jupyterlab/markdownviewer-extension:plugin - users will loose ability to open Markdown previews
• @jupyterlab/mathjax2-extension:plugin (if installed with optional jupyterlab-mathjax2 package) - an older version of the mathjax plugin for JupyterLab 4.x

To disable these extensions run:

jupyter labextension disable @jupyterlab/markdownviewer-extension:plugin
jupyter labextension disable @jupyterlab/mathjax-extension:plugin
jupyter labextension disable @jupyterlab/mathjax2-extension:plugin

To confirm that the plugins were disabled run:

jupyter labextension list

References

None

Notes

This change has a potential to break rendering of some markdown. There is a setting in Sanitizer which allows to revert to the previous sanitizer settings (allowNamedProperties).