Malicious code in css-field-sizing-polyfill (npm)

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

--- _-= Per source details. Do not edit below this line.=-_ ## Source: amazon-inspector (549bb8820cb6a8a35853826d17b64df14c0561b83790192a33c5dc76dbad53b9) The package advertises itself as a CSS field-sizing polyfill but ships thunderboltRegistry.js, which runs an IIFE at module load time. The IIFE shells out via child_process.execSync to run `id`, `whoami`, `uname -a`, `ifconfig`/`ip addr`, and `cat /etc/hosts`, then transmits the collected output together with hostname, Node version, platform, and pid as query-string parameters to the hardcoded plaintext endpoint http://dxpoc.gt.tc/callback.php/bb8968d0f67000433bf7005dd5ad2d1f. The module also exports proxied stubs for Wix-internal names (`thunderboltRegistry`, `siteAssetsRegistry`, `documentManagementRegistry`, `editorRegistry`, `corvidRegistry`) and ships a `registry-manifest.min.json` pointing at `static.parastorage.com`, indicating a dependency-confusion impersonation of Wix internal packages so that an internal resolver pulling this public name will trigger the beacon. The reconnaissance behavior is unrelated to the declared CSS polyfill purpose and fires on any `require()` of the package.

Source published

4 Oct 2026 23:14:01 UTC

Source modified

4 Oct 2026 23:30:06 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.