JupyterLab: Cross-site scripting (XSS) via crafted settings file (`overrides.json`)

Summary

jupyterlab is an extensible environment for interactive and reproducible computing, based on the Jupyter Notebook Architecture. From 3.3.0 until 4.5.10 and 4.6.2, JupyterLab allows notebook settings to be shared and applied through an overrides.json file using the Import button in the Settings Editor. In packages/notebook-extension/schema/tracker.json and packages/notebook-extension/src/index.ts, the sideBySideLeftMarginOverride and sideBySideRightMarginOverride settings are not properly validated before being inserted into style content, allowing a crafted settings file to contain instructions that execute as code instead of only changing display preferences. A user can import the malicious file, or an attacker with access to a shared settings location can plant an overrides.json that is applied automatically. The embedded code runs with the affected user's access and can read or modify notebooks and files and run code through the notebook server, including on a connected kernel. This issue is fixed in versions 4.5.10 and 4.6.2.

Timeline

1. Aug 13, 2026, 10:04 PM UTCCVE published
2. Aug 14, 2026, 4:06 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Aug 14, 2026, 4:06 PM UTCRecord last updated

Affected versions

• jupyterlab jupyterlab

  From 3.3.0 · fixed in 4.5.10; From 4.6.0 · fixed in 4.6.2

• jupyterlabPyPI

  From 3.3.0 · fixed in 4.5.10; From 4.6.0 · fixed in 4.6.2

• jupyterlabPyPI

  From 4.6.0 · fixed in 4.6.2

• jupyterlabPyPI

  From 3.3.0 · fixed in 4.5.10

References 10