Malicious code in cache-poisoning-pwn-demo (npm)
The npm package cache-poisoning-pwn-demo contains malicious code in its postinstall hook and main entry point that executes platform-specific calculator commands at install-time and import-time without user consent. The package is self-described as a supply-chain attack demonstration, but the delivery mechanism is a fully functional arbitrary-command executor.
- Disclosed
- Last updated
- Blast radius
- Any npm consumer installing cache-poisoning-pwn-demo or depending on it transitively; execution occurs at install-time and import-time in the installer's context.
- Ecosystems
- Attack vectors
- Affected entities
- cache-poisoning-pwn-demonpm package containing malicious postinstall hook and poisoned is-number module
The npm package cache-poisoning-pwn-demo was published with malicious code embedded in its postinstall hook and main entry point. The postinstall hook executes node -e \"try { require('./dist/postinstall.js'); } catch(e) {}\", which loads a bundled poisoned is-number module containing a top-level IIFE that unconditionally calls child_process.exec with platform-specific commands: open -a Calculator on macOS, calc.exe on Windows, and gnome-calculator/xcalc on Linux.\n\nThe same malicious IIFE is present in dist/index.js (the package's main entry point), meaning any consumer that requires or imports the package will also trigger arbitrary command execution. The package self-identifies as a supply-chain attack demonstration.\n\nWhile the current payload only spawns a calculator application, the underlying mechanism is a fully functional install-time and import-time arbitrary-command executor. Any installer running npm install or any downstream library that transitively requires this package will execute the hardcoded command in the installer's security context, demonstrating a real attack primitive.\n\nThe incident was identified and credited to the OpenSSF malicious-packages project.
Indicators of compromise
- Packages
- cache-poisoning-pwn-demo
Remediation
- Remove cache-poisoning-pwn-demo from all dependencies immediately
- Audit npm install logs and process execution history for evidence of command execution
- Review all transitive dependencies to identify if cache-poisoning-pwn-demo was pulled in as an indirect dependency
- Regenerate any credentials or secrets that may have been exposed during the installation window
- Update npm to the latest version and run `npm audit` to detect similar malicious packages
- Consider using npm package integrity verification and allowlist/denylist policies to prevent installation of known malicious packages
Sources
- GitHub Advisory GHSA-fg76-6277-9c5c · GitHub Advisory Database
Cite this entry
"Malicious code in cache-poisoning-pwn-demo (npm)." supplychainattack.org, Supply Chain Attack Incident Catalog. Disclosed July 27, 2026; last updated July 28, 2026. https://supplychainattack.org/incident/malicious-code-in-cache-poisoning-pwn-demo-npm-1r0pmk
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