Malicious code in css-reading-flow-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 (3b18e313d5fc67f07c1bcf051bd79a85dca97bb3c4510d9755efca6414bb55ff) The package is published as css-reading-flow-polyfill but ships thunderboltRegistry.js, which impersonates internal Wix thunderbolt registry modules (thunderboltRegistry, siteAssetsRegistry, documentManagementRegistry, editorRegistry, corvidRegistry, and others) by exporting all of those names from a single payload file. On require, an IIFE in thunderboltRegistry.js uses child_process.execSync to run id, whoami, uname, ifconfig/ip-addr and read /etc/hosts, then fetches http://dxpoc.gt.tc/callback.php/bb8968d0f67000433bf7005dd5ad2d1f over plain HTTP with the command output, hostname, Node version, platform and pid appended as query parameters. The module also walks require.cache and deletes any entry whose key contains 'thunderboltRegistry' so the recon-and-exfil IIFE re-runs on every require rather than being cached. index.js is an empty decoy; the stated CSS polyfill purpose is a cover story and the package has no implementation of that functionality.

Source published

4 Oct 2026 23:15:00 UTC

Source modified

4 Oct 2026 23:30:04 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.