CVE-2026-67338
JupyterLab: Stored XSS in extension manager through package metadata unsanitized URI protocol
Published Jun 19, 2026 · updated Oct 14, 2026
A malicious PyPI package can place a URL in its metadata. JupyterLab's Extension Manager renders this as the extension's home-page link without validating the protocol, so a user who clicks the extension name executes attacker-controlled JavaScript in the JupyterLab origin. ### Details One of the PyPI package's URL (jupyterlab/extensions/pypi.py) is copied straight into the rendered by the frontend in packages/extensionmanager/src/widget.tsx#L77-L88. ### Impact An attacker needs to publish a package to PyPI (no access to the target). When the package appears in a victim's extension manager list and the victim clicks the extension name, the payload runs in the JupyterLab origin. Preconditions: Extension Manager enabled with the default PyPI source, the malicious package appears in the victim's list/search results. ### Patches Patched in [4.5.9](https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.9), commits [4e61e07](https://github.com/jupyterlab/jupyterlab/commit/4e61e07d0a91145b53fbf96ac74b0387f6bc51f6) and [d5d961f](https://github.com/jupyterlab/jupyterlab/commit/d5d961f6e10a6442dddbf94d9a976b3897055a12)
Timeline
Detection, updates, and resolution for this record.
Jun 19, 2026 · GitHub Advisory Database
Detected
A malicious PyPI package can place a URL in its metadata. JupyterLab's Extension Manager renders this as the extension's home-page link without validating the protocol, so a user who clicks the extension name executes attacker-controlled JavaScript in the JupyterLab origin. ### Details One of the PyPI package's URL (jupyterlab/extensions/pypi.py) is copied straight into the rendered by the fronten
Oct 14, 2026 · GitHub Advisory Database
Fix available
jupyterlab fixed in 4.5.9
Oct 14, 2026 · GitHub Advisory Database
Fix available
jupyterlab fixed in 4.5.9
Oct 14, 2026 · GitHub Advisory Database
Updated
A malicious PyPI package can place a URL in its metadata. JupyterLab's Extension Manager renders this as the extension's home-page link without validating the protocol, so a user who clicks the extension name executes attacker-controlled JavaScript in the JupyterLab origin. ### Details One of the PyPI package's URL (jupyterlab/extensions/pypi.py) is copied straight into the rendered by the fronten
Affected
- PyPI jupyterlab0 → 4.5.9
Sources
- CVE.orgCVE-2026-67338
Official CVE identifier
cve.org - FIRST EPSSCVE-2026-67338
30-day exploitation probability 0.3%
first.org - GitHub Advisory DatabaseGHSA-vmhf-c436-hxj4
GitHub Advisory Database record mirrored by OSV.
github.com - OSV.devGHSA-vmhf-c436-hxj4
JupyterLab: Stored XSS in extension manager through package metadata unsanitized URI protocol
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