JupyterLab before 4.5.9 contains a stored cross-site scripting vulnerability in the Extension Manager. The vulnerability fails to validate URI protocols in package metadata URLs, allowing attackers to publish malicious PyPI packages with javascript: URLs in project metadata. These URLs can execute arbitrary JavaScript in the JupyterLab origin when users click the extension name. This vulnerability can be [truncated]
The JupyterLab Git extension for JupyterLab, from version 0.30.0b3 before 0.54.0, contains a vulnerability. The PlainTextDiff.ts createHeader() method passes Git filenames directly to innerHTML when rendering renamed files in commit history. This allows a crafted filename to execute JavaScript when a victim views the rename diff in the Git History tab.
CVE-2026-42266 affects JupyterLab versions 4.0.0 through 4.5.6. The issue is an enforcement failure in the PyPI Extension Manager allow-list: allowed_extensions_uris is not correctly enforced, and the Extension Manager was not contained to packages listed on the default PyPI index. The issue is fixed in JupyterLab 4.5.7. Based on the published CVSS vector, this is a high-severity issue with network attack [truncated]
