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lean-ctx-bin@3.9.18: Malicious npm security report (Block) | LPM Firewall

registry / lean-ctx-bin / 3.9.18

lean-ctx-bin@3.9.18

LeanCTX — the Context OS for AI coding agents. One local binary that compresses, remembers, routes, and verifies every token between your code and the model. No Rust required.

AI Security Review

scanned 6d ago · by lpm-firewall-ai

npm postinstall downloads a remote native payload, installs it, and executes its onboarding action automatically. The downloaded binary is not bundled for source inspection and is selected from the repository's mutable latest release.

Static reason

One or more suspicious static signals were detected.; previous stored version diff introduced dangerous source

Trigger

npm install of lean-ctx-bin outside CI unless LEAN_CTX_NO_ONBOARD=1 is set.

Impact

Arbitrary code from a later GitHub release runs during installation and may alter AI-tool/MCP configuration through automatic onboarding.

Mechanism

install-time remote native payload download, extraction, and execution

Attack narrative

During npm postinstall, the package queries the latest GitHub release, downloads a platform archive, extracts its native executable into its bin directory, then runs that executable with onboard. This is unconsented install-time execution of mutable remote code; the package source cannot establish what the downloaded binary does. The documented product scope includes AI-tool and MCP configuration.

Rationale

This package creates a concrete install-time remote-code-execution path and automatically invokes an AI-tool onboarding operation. Optional checksum comparison does not bind the payload to the reviewed package version because both release metadata and checksum are fetched at install time.

Evidence

package.jsonpostinstall.jsREADME.mdbin/lean-ctx.jsbin/lean-ctxbin/lean-ctx.exetemporary lean-ctx archive directory

Network endpoints2

Source & flagged code

5 flagged · loading source

package.jsonView file

•scripts.postinstall = node postinstall.js

High

Install Time Lifecycle Scripts

Package defines install-time lifecycle scripts.

package.jsonView on unpkg

6scripts.postinstall = node postinstall.js Install-time code downloads an unverified remote native archive, stages it locally, activates an executable path, and exposes it to process execution. L6: const path = require("path"); L7: const https = require("https"); L8: const { createGunzip } = require("zlib"); L9: const crypto = require("crypto"); ... L31: L32: function getTarget() { L33: const platform = process.platform; ... L42: const archMap = { x64: "x86_64", arm64: "aarch64" }; L43: const rustArch = archMap[arch]; L44: if (!rustArch) { L45: console.error(`Unsupported architecture: ${arch}`); ... L47: }

High

Unverified Remote Native Payload Install

Install-time source downloads a native archive from a fixed external host without transport verification, extracts it, and installs an executable payload.

package.jsonView on unpkg · L6

•scripts.postinstall = node postinstall.js

Medium

Ambiguous Install Lifecycle Script

Install-time lifecycle script is not statically allowlisted and needs review.

package.jsonView on unpkg

postinstall.jsView file

3L4: const { execSync } = require("child_process"); L5: const fs = require("fs"); L6: const path = require("path"); L7: const https = require("https"); L8: const { createGunzip } = require("zlib"); L9: const crypto = require("crypto"); ... L11: const REPO = "yvgude/lean-ctx"; L12: const BIN_DIR = path.join(__dirname, "bin"); L13: const IS_WIN = process.platform === "win32"; L14: const BINARY_NAME = IS_WIN ? "lean-ctx.exe" : "lean-ctx"; ... L128: lastPct = pct;

High

Install Named Payload File

Install-named source file stages remote content through filesystem writes and execution.

postinstall.jsView on unpkg · L3

•matchType = previous_version_dangerous_delta matchedPackage = lean-ctx-bin@3.9.12 matchedIdentity = npm:bGVhbi1jdHgtYmlu:3.9.12 similarity = 0.500 summary = stored previous version shares package body but lacks this dangerous source file

High

Previous Version Dangerous Delta

This package version adds a dangerous source file absent from the previous stored version; route for source-aware review.

postinstall.jsView on unpkg