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yu-method@1.1.4: Malicious npm security report (Block) | LPM Firewall

registry / yu-method / 1.1.4

yu-method@1.1.4

YU-METHOD — personal agile AI development skills built on BMAD-METHOD with customizable hooks

AI Security Review

scanned 1mo ago · by lpm-firewall-ai

Installing the package runs an unprompted postinstall hook that modifies global AI-agent skill and instruction surfaces. It also installs and registers an MCP server in the user's Claude configuration.

Static reason

High-risk behavior combination matched malicious policy.; source matched previously finalized malicious package; routed for review; source fingerprint signature matched known malicious package; routed for review

Trigger

npm installation of yu-method

Impact

The package changes how Claude, Codex, and other agent environments load skills and respond to future prompts without an explicit setup command.

Mechanism

Postinstall mutation of global agent skills, instructions, and MCP configuration

Attack narrative

On npm installation, package.json invokes scripts/install.js. That hook copies its bundled skills into global directories for multiple AI-agent products, installs a separate global package, registers it as a Claude MCP server, and appends rules to Claude and Codex instruction files. The inserted rules direct agents to invoke package skills automatically before handling certain future user messages. These are broad, persistent AI-agent control-surface changes performed without an explicit user setup action.

AI rationale

The automatic lifecycle hook makes broad, persistent changes to foreign AI-agent control surfaces and installs an additional global package. This meets the install-hook abuse boundary regardless of the absence of direct credential theft.

Evidence

package.jsonscripts/install.js~/.claude/skills/yu-*~/.agents/skills/yu-*~/.codex/skills/yu-*~/.claude.json~/.claude/CLAUDE.md

Source & flagged code

10 flagged · loading source

package.jsonView file

•scripts.postinstall = node scripts/install.js

High

Install Time Lifecycle Scripts

Package defines install-time lifecycle scripts.

package.jsonView on unpkg

•scripts.postinstall = node scripts/install.js

Medium

Ambiguous Install Lifecycle Script

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

package.jsonView on unpkg

scripts/brain-setup.jsView file

6const os = require('os'); L7: const { spawnSync } = require('child_process'); L8: const readline = require('readline');

High

Child Process

Package source references child process execution.

scripts/brain-setup.jsView on unpkg · L6

•matchType = normalized_sha256 matchedPackage = yu-method@1.0.0 matchedPath = scripts/brain-setup.js matchedIdentity = npm:eXUtbWV0aG9k:1.0.0 similarity = 1.000 summary = normalized source hash matched finalized malicious source

High

Known Malware Source Similarity

Source file is highly similar to a previously finalized malicious package; route for source-aware review.

scripts/brain-setup.jsView on unpkg

•matchType = malicious_source_fingerprint_signature signature = 67385636f38de6e9 signatureType = suspicious_hashes sourceLabel = final_verdict:malicious matchedPackage = yu-method@1.1.1 matchedPath = scripts/brain-setup.js matchedIdentity = npm:eXUtbWV0aG9k:1.1.1 similarity = 1.000 shingleOverlap = 8 summary = package final verdict is malicious

High

Known Malware Source Fingerprint Signature

Source fingerprint signature matches a known malicious package signature; route for source-aware review.

scripts/brain-setup.jsView on unpkg

scripts/install.jsView file

8L9: const CLAUDE_SKILLS_DIR = path.join(os.homedir(), '.claude', 'skills'); L10: const AGENTS_SKILLS_DIR = path.join(os.homedir(), '.agents', 'skills'); L11: const CODEX_SKILLS_DIR = path.join(os.homedir(), '.codex', 'skills'); L12: const OWN_SKILLS_DIR = path.join(__dirname, '..', 'skills'); ... L16: function copyDir(src, dest) { L17: fs.mkdirSync(dest, { recursive: true }); L18: for (const entry of fs.readdirSync(src, { withFileTypes: true })) { ... L21: if (entry.isDirectory()) copyDir(srcPath, destPath); L22: else fs.copyFileSync(srcPath, destPath); L23: } ... L40: c = c.replace(/^document_output_language:\s*.+$/m, 'document_output_language: Chinese');

Critical

Ai Agent Control Hijack

Source creates an unconsented AI-agent control surface through install-time mutation or a default unauthenticated remote skill channel.

scripts/install.jsView on unpkg · L8

•Manifest-trigger-reachable source links an external AI-agent control path to a behavior-bearing write operation. #!/usr/bin/env node 'use strict'; const fs = require('fs'); const path = require('path'); const os = require('os'); const { spawnsync } = require('child_process'); const claude_skills_dir = path.join(os.homedir(), '.claude', 'skills'); const agents_skills_dir = path.join(os.homedir(), '.agents', 'skills'); const codex_skills_dir = path.join(os.homedir(), '.codex', 'skills'); const own_skills_dir = path.join(__dirname, '..', 'skills'); const bmad_sentinel = path.join(claude_skills_dir, 'bmad-dev-story'); function copydir(src, dest) { fs.mkdirsync(dest, { recursive: true }); for (const

High

Trigger Reachable External Ai Agent Control Surface Mutation

Manifest-trigger-reachable source writes behavior-bearing configuration into a user or project AI-agent control surface.

scripts/install.jsView on unpkg

scripts/session-end-hook.shView file

•path = scripts/session-end-hook.sh kind = build_helper sizeBytes = 1150 magicHex = [redacted]

Medium

Ships Build Helper

Package ships non-JavaScript build or shell helper files.

scripts/session-end-hook.shView on unpkg

scripts/brain-setup.js#virtual:normalized:round1View file

•stage = ast_semantic_analysis; reason = ast_parse_error; limitedFiles = 2

High

Semantic Analysis Limited

A bounded semantic-analysis stage reached its safety limit; remaining detectors completed, but this package requires AI review.

scripts/brain-setup.js#virtual:normalized:round1View on unpkg