OpenSSF/OSV advisory MAL-2026-6718 confirms this npm version as malicious. package.json declares `bin: { "node": "./shim.js" }`, causing `npm`/`yarn` to symlink `node` in `node_modules/.bin` (and in a system bin dir on global install) to a package-controlled script. Subsequent invocations of `node` resolved through that PATH entry execute shim.js instead of the real Node.js runtime, redirecting any tooling that expects `node` to attacker-controlled code. In addition, `scripts.postinstall`...
Source
OpenSSF Malicious Packages via OSV
Summary
Malicious code in test-pkg-yarn (npm)
Details
package.json declares `bin: { "node": "./shim.js" }`, causing `npm`/`yarn` to symlink `node` in `node_modules/.bin` (and in a system bin dir on global install) to a package-controlled script. Subsequent invocations of `node` resolved through that PATH entry execute shim.js instead of the real Node.js runtime, redirecting any tooling that expects `node` to attacker-controlled code. In addition, `scripts.postinstall` runs `bun shim.js || node shim.js`, and shim.js unconditionally invokes OS commands at install time via `child_process.execSync` — spawning a GUI calculator (`calc` on Windows, `gnome-calculator` on Linux, `open -a Calculator` on macOS), opening a URL in the user's browser, and writing a marker file to `/tmp/.bun-npm-pwned`. The package self-identifies as 'BunnyHijack PoC - yarn variant' with the console message '[!] PATH POISONED - test-pkg-yarn just hijacked your node command.' Although framed as a proof-of-concept and not currently exfiltrating data, the behavior is real install-time code execution against any developer who installs the package and a persistent hijack of the `node` command in PATH.
Decision reason
OpenSSF Malicious Packages via OSV confirms test-pkg-yarn@1.0.0 as malicious (MAL-2026-6718): Malicious code in test-pkg-yarn (npm)