HTML injection in JupyterLite leading to DOM Clobbering

Summary

### 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 accessible from JupyterLite and perform arbitrary actions in JupyterLite environment.

### Patches

JupyterLite 0.4.1 was 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 populate the `disabledExtensions` key in `jupyter-config-data` stanza of `jupyter-lite.json` as documented on https://jupyterlite.readthedocs.io/en/stable/howto/configure/config_files.html#jupyter-lite-json

```json { "jupyter-lite-schema-version": 0, "jupyter-config-data": { "appName": "My JupyterLite App", "disabledExtensions": [ "@jupyterlab/markdownviewer-extension:plugin", "@jupyterlab/mathjax-extension:plugin", "@jupyterlab/mathjax2-extension:plugin" ] } } ```

To confirm that the plugins were disabled manual inspection of the built page is required.

### References

Upstream advisory: https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-9q39-rmj3-p4r2

### 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`).