MAL-2026-16032 Malicious code in feishu-docx-mcp (npm)

package.json declares "preinstall": "bun run index.js" and lists bun as a runtime dependency, so npm install fetches the alternate Bun runtime and executes the tarball's top-level index.js on the installer machine. index.js is a ~499KB file packed with obfuscator.io (rotating string array of 1732 entries, hex-named identifiers, decoder wrappers) plus a custom RC4/XOR cipher class keyed via pbkdf2Sync(seed, salt, 200000, 32, 'sha256') and exposed as a global decrypt function to reconstruct strings at runtime. After deobfuscation the payload contains GitHub Personal Access Token validation and scope enumeration logic: Authorization: Bearer <token> requests to /user and /user/orgs, parsing of the x-oauth-scopes response header, and checks for repo, public_repo, and workflow scopes plus github-authentication-token-expiration. The advertised functionality is a Feishu/Lark document MCP server, whose shipped code lives in dist/ and is unrelated to the obfuscated top-level index.js that only preinstall runs. Bundling an alternate runtime purely to execute an obfuscated install-time blob that fingerprints GitHub credentials is the canonical alternate-runtime-dropper shape of an npm supply-chain attack.

Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.