CVE-2025-59842: JupyterLab: missing noopener enables reverse tabnabbing

Links generated with LaTeX typesetters in Markdown files and Markdown cells in JupyterLab and Jupyter Notebook did not include the `noopener` attribute. This is deemed to have no impact on the default installations. Theoretically users of third-party LaTeX-rendering extensions could find themselves vulnerable to reverse tabnabbing attacks if: - links generated by those extensions included `target=_blank` (no such extensions are known at time of writing) and - they were to click on a link generated in LaTeX (typically visibly different from other links). For consistency with handling on other links, new versions of JupyterLab will enforce `noopener` and `target=_blank` on all links generated by typesetters. The former will harden the resilience of JupyterLab to extensions with lack of secure defaults in link rendering, and the latter will improve user experience by preventing accidental state loss when clicking on links rendered by LaTeX typesetters. ### Impact Since the official LaTeX typesetter extensions for JupyterLab: `jupyterlab-mathjax` (default), `jupyterlab-mathjax2` and `jupyterlab-katex` do not include the `target=_blank`, there is no impact for JupyterLab users. ### Patches JupyterLab 4.4.8 ### Workarounds No workarounds are necessary. ### References None

An adversary publishes a malicious JupyterLab LaTeX rendering extension to PyPI or npm that injects target=_blank into rendered links. A data scientist installs it to enable a specific LaTeX rendering feature. When they open a notebook containing LaTeX-rendered hyperlinks and click one, window.opener remains accessible to the destination page. The adversary's server detects the window.opener reference and silently redirects the original JupyterLab tab to a convincing fake login page, harvesting the researcher's credentials — which may include API keys for LLM services, model registries, or cloud ML platforms.