CVE-2026-42557

jupyterlab is an extensible environment for interactive and reproducible computing, based on the Jupyter Notebook Architecture. Prior to 4.5.7, JupyterLab’s HTML sanitizer allowlists data-commandlinker-command and data-commandlinker-args on button elements, while CommandLinker listens for all click events on document.body and executes the named command without checking whether the element came from trusted JupyterLab UI. A notebook with a pre-saved HTML cell output containing a deceptive button can trigger arbitrary JupyterLab commands – including arbitrary code execution – on a single user click, without any code being submitted for execution by the user. This vulnerability is fixed in 4.5.7.

More information : https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-mqcg-5×36-vfcg