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GHSA-VMHF-C436-HXJ4

Vulnerability from github – Published: 2026-06-19 15:11 – Updated: 2026-06-19 15:11
VLAI
Summary
JupyterLab: Stored XSS in extension manager through package metadata unsanitized URI protocol
Details

A malicious PyPI package can place a javascript: URL in its [project.urls] 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 homepage_url rendered by the frontend in packages/extensionmanager/src/widget.tsx#L77-L88.

best_guess_home_url = (
    homepage_url            # home_page / [project.urls] Homepage
    or data.get("project_url")
    or data.get("package_url")
    or documentation_url    # docs_url / [project.urls] Documentation
    or source_url           # [project.urls] Source Code
    or bug_tracker_url      # bugtrack_url / [project.urls] Bug Tracker
)

# homepage_url=best_guess_home_url

{entry.homepage_url ? (
  <a href={entry.homepage_url} target="_blank" rel="noopener noreferrer" ...>
    {entry.name}
  </a>
) : ( <div>{entry.name}</div> )}

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, commits 4e61e07 and d5d961f

Severity
5.1 (Medium)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 4.5.8"
      },
      "package": {
        "ecosystem": "PyPI",
        "name": "jupyterlab"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.5.9"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-84"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-19T15:11:17Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "A malicious PyPI package can place a `javascript:` URL in its `[project.urls]` metadata. JupyterLab\u0027s Extension Manager renders this as the extension\u0027s home-page link without validating the protocol, so a user who clicks the extension name executes attacker-controlled JavaScript in the JupyterLab origin.\n\n### Details\n\nOne of the PyPI package\u0027s URL (jupyterlab/extensions/pypi.py) is copied straight into the `homepage_url` rendered by the frontend in packages/extensionmanager/src/widget.tsx#L77-L88.\n\n```python\nbest_guess_home_url = (\n    homepage_url            # home_page / [project.urls] Homepage\n    or data.get(\"project_url\")\n    or data.get(\"package_url\")\n    or documentation_url    # docs_url / [project.urls] Documentation\n    or source_url           # [project.urls] Source Code\n    or bug_tracker_url      # bugtrack_url / [project.urls] Bug Tracker\n)\n\n# homepage_url=best_guess_home_url\n```\n\n```tsx\n{entry.homepage_url ? (\n  \u003ca href={entry.homepage_url} target=\"_blank\" rel=\"noopener noreferrer\" ...\u003e\n    {entry.name}\n  \u003c/a\u003e\n) : ( \u003cdiv\u003e{entry.name}\u003c/div\u003e )}\n```\n\n### Impact\n\nAn attacker needs to publish a package to PyPI (no access to the target). When the package appears in a victim\u0027s extension manager list and the victim clicks the extension name, the payload runs in the JupyterLab origin.\n\nPreconditions: Extension Manager enabled with the default PyPI source, the malicious package appears in the victim\u0027s list/search results.\n\n### Patches\nPatched 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)",
  "id": "GHSA-vmhf-c436-hxj4",
  "modified": "2026-06-19T15:11:17Z",
  "published": "2026-06-19T15:11:17Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/jupyterlab/jupyterlab/security/advisories/GHSA-vmhf-c436-hxj4"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jupyterlab/jupyterlab/commit/4e61e07d0a91145b53fbf96ac74b0387f6bc51f6"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jupyterlab/jupyterlab/commit/d5d961f6e10a6442dddbf94d9a976b3897055a12"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/jupyterlab/jupyterlab"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jupyterlab/jupyterlab/releases/tag/v4.5.9"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "JupyterLab: Stored XSS in extension manager through package metadata unsanitized URI protocol"
}



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