Malicious code in studiocode_tools (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 (261d413c0847b530c9a452c209c25e0a7d9123f9b0f20b26d0afcc41a929c74a) package.json declares a postinstall hook that runs `wscript.exe 4444.vbs`, auto-executing on `npm install` on Windows. The shipped 4444.vbs contains hand-rolled AES and ChaCha20 implementations with XOR-obfuscated S-boxes, SHA-256 round constants XORed with 0x5A5A5A5A, and hundreds of base64 ciphertext fragments (`ArtifactBundleHX`) that are reassembled and decrypted at runtime into a PowerShell loader. The script writes a payload file to `%TEMP%\pfNNNNN.dat` and invokes `powershell.exe` to perform process hollowing of the decrypted payload. The VBS carries cover-story branding as 'Verdant Signals Corp' / 'Device Telemetry Aggregator', and the README falsely states 'There are no installation scripts.' The multi-layer custom cryptography, false branding, and explicit README denial of install scripts are unambiguous indicators of hostile intent rather than legitimate functionality.

Source published

4 Oct 2026 23:25:54 UTC

Source modified

4 Oct 2026 23:45:19 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.