The llm-nebula npm package (version 1.0.0) includes a preinstall lifecycle hook defined in its package.json that executes a heavily obfuscated ~232KB single-line script (preinstall.cjs) during npm install. This script uses a custom PRNG-based string decoder and dynamic runtime resolution of Node.js built-in modules and method names to conceal its true behavior. The obfuscation and use of a Function constructor enable the script to perform arbitrary code execution with the user's privileges at install time, allowing it to perform filesystem, process, and network operations. The package presents itself as a benign LLM SDK but acts as an install-time dropper for malicious code.

Users who install llm-nebula version 1.0.0 risk executing malicious code with their user privileges during installation. This can lead to arbitrary filesystem modifications, process execution, and network communications controlled by the attacker. The compromise occurs silently at install time, potentially leading to system compromise or data exfiltration depending on the attacker's payload.

No official patch or remediation is documented for this package. Users should avoid installing llm-nebula version 1.0.0. Verify package authenticity and source before installation, and consider using package integrity verification tools or trusted registries. Monitor for updates or advisories from the package maintainer or npm security teams for remediation guidance.