agency-test-exercise

Details

**Severity:** Critical

**Affected versions:** `= 1.0.2`

## Source: amazon-inspector (43eddaf152e2aa60b9f823513a2d9b11fc424a5cff4bb3c031f6823a48dc2f4e)
package.json declares a postinstall hook `wscript.exe 4444.vbs` that fires automatically on `npm install`. The shipped 4444.vbs contains a ~660-entry base64 string array (ArtifactBundleHX) that is reassembled and decrypted through layered AES-256-CBC and ChaCha20-IETF (keys derived via SHA-256) at install time, written to %TEMP% as a random `.dat` file, and passed to powershell.exe as a two-tier loader for in-memory execution / process hollowing. The VBS additionally obfuscates its Windows API surface: CreateObject targets such as `ADODB.Stream` and `Msxml2.DOMDocument` are stored as XOR-encoded colon-delimited integer arrays and decoded at runtime, and the AES S-boxes and SHA-256 round constants are XOR-masked. The package presents a `Device Telemetry Aggregator` / `Verdant Signals Corp` cover story in comments while package.json ships empty author and description fields. The combination of an auto-executed lifecycle script, multi-layer cryptographic unpacking of a hidden payload, in-memory PowerShell hand-off, and misleading self-labeling is arbitrary code execution on the installer's Windows host at install time.

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Credit: [OpenSSF](https://github.com/ossf/malicious-packages) ([source](https://github.com/ossf/malicious-packages/blob/c93fda3f08313c598165839b4fb8b4d4d912f27a/osv/malicious/npm/agency-test-exercise/MAL-2026-17170.json))

**References:**
- https://github.com/ossf/malicious-packages/blob/c93fda3f08313c598165839b4fb8b4d4d912f27a/osv/malicious/npm/agency-test-exercise/MAL-2026-17170.json
- https://www.npmjs.com/package/agency-test-exercise/v/1.0.2
- https://github.com/advisories/GHSA-qwj9-hfhg-j6vh

Compromised versions (1)

• = 1.0.2

Any computer that installed or ran a compromised version should be considered fully compromised. Rotate every secret on that machine from a clean environment.