Malicious code in css-nesting-transform (npm)

{
  "id": "3f7b34674c09ee50cd1a292b8437333dec339490bedfdcd70198d175896bae0c",
  "url": "https://osv.dev/vulnerability/MAL-2026-17804",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Malicious code in css-nesting-transform (npm)",
    "summary": "css-nesting-transform@1.0.0 was published to npm on 2026-10-07 01:32 UTC by user brahimhamidi (the same account that published css-flow-render-shim@1.0.0 on 2026-10-06). It is described as a CSS polyfill but contains none: index.js is an empty module (byte-identical to the index.js of css-jptvix-polyfill@1.0.0) and payload.min.css is 29 bytes. payload.bundle.min.js carries the payload and runs at require time as a top-level IIFE; it first deletes its own require.cache entries so that it runs again on every require. Module names, commands and URLs are encoded as numeric arrays and decoded at runtime. Behavior: (1) obtains child_process to execute system commands; (2) runs whoami, id and uname -a with execSync and sends each output, together with os.hostname() and the tag vector=registryLibrariesTopology, to https://webhook.site/69bcd627-1871-4dda-b880-83b37ceac418 through both fetch and https.get; (3) sends a beacon tagged topology-rce-v7 with the Node version, platform, process id and timestamp; (4) exports Proxy objects under Wix-internal module names (thunderboltRegistry, siteAssetsRegistry, documentManagementRegistry, editorRegistry, corvidRegistry, dataBindingRegistry, autoCompleteRegistry, thunderboltBuilderRegistry, thunderboltPreviewRegistry), and the two rb_*.thunderbolt.manifest.min.json files list the payload under https://unpkg.com/css-nesting-transform@1.0.0/, which indicates a dependency-confusion attempt against that organization's private packages. Trigger: on ",
    "evidence": "osv:MAL-2026-17804",
    "products": [
      {
        "name": {
          "value": "css-nesting-transform",
          "evidence": "/affected/0/package/name"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": [
          {
            "value": "1.0.0",
            "evidence": "/affected/0/versions"
          }
        ]
      }
    ],
    "severity": "unknown",
    "structured": {
      "id": "MAL-2026-17804",
      "aliases": [
        "MAL-2026-17804"
      ],
      "affected": [
        {
          "package": {
            "name": "css-nesting-transform",
            "purl": "pkg:npm/css-nesting-transform",
            "ecosystem": "npm"
          },
          "versions": [
            "1.0.0"
          ],
          "database_specific": {
            "source": "https://github.com/ossf/malicious-packages/blob/main/osv/malicious/npm/css-nesting-transform/MAL-2026-17804.json"
          }
        }
      ],
      "modified": "2026-10-12T04:45:05.841910541Z",
      "provider": "osv",
      "references": [],
      "provider_metadata": {
        "iocs": {
          "urls": [
            "https://webhook.site/69bcd627-1871-4dda-b880-83b37ceac418"
          ],
          "files": [
            {
              "note": "payload: runs on require, executes whoami, id and uname -a and sends the output to webhook.site",
              "paths": [
                "payload.bundle.min.js"
              ],
              "source": "PACKAGE_ARCHIVE",
              "digests": {
                "sha256": "225cc9416e39883c2390e604d2ef10cbde572f909d52abf3ddc2361b220f6a18"
              }
            },
            {
              "note": "manifest in Wix thunderbolt format pointing at this package on unpkg (dependency confusion)",
              "paths": [
                "rb_wixui.thunderbolt.manifest.min.json"
              ],
              "source": "PACKAGE_ARCHIVE",
              "digests": {
                "sha256": "6452b9044a064b07500e758cf348f72d20b65429a020ab0d01dc15c0230240c9"
              }
            }
          ],
          "domains": [
            "webhook.site"
          ]
        }
      }
    },
    "related_cves": [],
    "security_relevant": true,
    "severity_evidence": null
  },
  "source_id": "core-osv",
  "document_id": 298561,
  "published_at": "2026-10-08T06:00:00+00:00"
}