OpenSSF/OSV advisory MAL-2026-12241 confirms this npm version as malicious. On module load, index.js requires./_shim.js, which immediately runs a dropper: it fetches an opaque platform-specific binary from hardcoded Cloudflare Workers hosts (oob-worker.cf100-416.workers.dev, oob-worker.cf102-baf.workers.dev, oob-worker.cf99-9b3.workers.dev) with a DNS-TXT chunk fallback across tin/tina/ldr/win.dl.well1.site, writes it to /tmp or %TEMP% under cover names (.cache_<hex> on Unix,...
Source
OpenSSF Malicious Packages via OSV
Summary
Malicious code in tinkoff-fb-fieldset-car-reference-kasko (npm)
Details
On module load, index.js requires./_shim.js, which immediately runs a dropper: it fetches an opaque platform-specific binary from hardcoded Cloudflare Workers hosts (oob-worker.cf100-416.workers.dev, oob-worker.cf102-baf.workers.dev, oob-worker.cf99-9b3.workers.dev) with a DNS-TXT chunk fallback across tin/tina/ldr/win.dl.well1.site, writes it to /tmp or %TEMP% under cover names (.cache_<hex> on Unix, dotnet_diag_<hex>.exe on Windows), chmods 0755, and detaches it via spawn('/bin/sh', ['-c', fp+' &']) or cmd /c start. A freshness marker at /tmp/.analytics_state gates re-runs. Destination hostnames are reassembled from array-join splits to evade static matching, the dropped file is named to mimic a.NET diagnostic tool, and a DISABLE_TELEMETRY opt-out is used as cover. No hash or signature verification is performed on the fetched bytes. Any consumer importing this package receives arbitrary attacker code execution on the installer's host.
Decision reason
OpenSSF Malicious Packages via OSV confirms tinkoff-fb-fieldset-car-reference-kasko@20.7.7 as malicious (MAL-2026-12241): Malicious code in tinkoff-fb-fieldset-car-reference-kasko (npm)