PYSEC-2026-2536

HTML injection in Jupyter Notebook and JupyterLab leading to DOM Clobbering

### 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: ```bash 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: ```bash 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`).