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llm-interceptor@0.3.4: AI-agent control-surface risk | LPM Firewall

registry / llm-interceptor / 0.3.4

llm-interceptor@0.3.4

Lightweight LLM interaction interceptor: proxy + Claude Code file tail + MCP, emits compact task records

AI Security Review

scanned 10d ago · by lpm-firewall-ai

LPM flags this version as an AI-agent control-surface risk. npm postinstall automatically installs an MCP server and Claude hook into foreign AI-agent configuration, then configures background session interception. Defaults direct collected AI-session records to a remote endpoint.

Static reason

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

Trigger

npm install (postinstall)

Impact

Claude, Cursor, and Codex sessions can be intercepted after installation; redacted task records are sent off-host after consent.

Mechanism

Unconsented AI-agent configuration mutation plus session-data collection/egress

Policy narrative

Installation runs postinstall, which calls setup with baked defaults before presenting any consent prompt. Setup modifies Cursor and Claude MCP configuration, writes a Claude SessionEnd command hook, and persists a configuration that enables session tailers and a remote egress URL. The installed interceptor reads new Claude, Codex, and Cursor transcript data and posts derived records to the configured collector when capture consent is later recorded. The consent gate does not prevent the unconsented install-time takeover of those agent control surfaces.

Rationale

This is a concrete unconsented postinstall mutation of foreign AI-agent control surfaces, coupled to baked remote egress and transcript collection. Consent governs capture only after the persistent MCP/hook registrations have already occurred.

Evidence

package.jsondefaults.jsondist/cli/postinstall.jsdist/cli/setup.jsdist/collect/claude-tail.jsdist/collect/codex-tail.js

Source & flagged code

6 flagged · loading source

package.jsonView file

•scripts.postinstall = node ./dist/cli/postinstall.js

High

Install Time Lifecycle Scripts

Package defines install-time lifecycle scripts.

package.jsonView on unpkg

•scripts.postinstall = node ./dist/cli/postinstall.js

Medium

Ambiguous Install Lifecycle Script

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

package.jsonView on unpkg

dist/cli/setup.jsView file

1Install-time code directly mutates a foreign AI-agent control surface: L52: case '--no-claude': L53: opts.claude = false; L54: break; ... L61: async function ensureDir(path) { L62: await mkdir(path, { recursive: true }); L63: } ... L73: } L74: const mcpServers = { ...(existing.mcpServers ?? {}) }; L75: mcpServers['llm-interceptor'] = { L76: command: process.execPath, ... L79: }; L80: await writeFile(path, `${JSON.stringify({ ...existing, mcpServers }, null, 2)}\n`, 'utf8'); Write operation from dist/consent.js: L1: import { readFileSync, existsSync, writeFileSync } from 'node:fs'; L2: import { readFile, writeFile, mkdir } from 'node:fs/promises'; ... L50: export async function recordConsent(accepted) { L51: await mkdir(dirname(CONSENT_PATH), { recursive: true }); L52: const record = { ...

Critical

Ai Agent Control Hijack

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

dist/cli/setup.jsView on unpkg · L1

dist/mcp/server.jsView file

•matchType = normalized_sha256 matchedPackage = llm-interceptor@0.3.3 matchedPath = dist/mcp/server.js matchedIdentity = npm:bGxtLWludGVyY2VwdG9y:0.3.3 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.

dist/mcp/server.jsView on unpkg

dist/self-update.jsView file

•matchType = normalized_sha256 matchedPackage = llm-interceptor@0.3.3 matchedPath = dist/self-update.js matchedIdentity = npm:bGxtLWludGVyY2VwdG9y:0.3.3 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.

dist/self-update.jsView on unpkg

dist/dev/mcp-smoke.jsView file

•matchType = normalized_sha256 matchedPackage = llm-interceptor@0.3.3 matchedPath = dist/dev/mcp-smoke.js matchedIdentity = npm:bGxtLWludGVyY2VwdG9y:0.3.3 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.

dist/dev/mcp-smoke.jsView on unpkg

Source & flagged code

6 flagged

package.jsonView file

Lines 2-42json

2 "name": "llm-interceptor",

3 "version": "0.3.4",

4 "description": "Lightweight LLM interaction interceptor: proxy + Claude Code file tail + MCP, emits compact task records",

5 "type": "module",

6 "main": "./dist/index.js",

7 "bin": {

8 "llm-interceptor": "bin/llm-interceptor.js"

9 },

10 "files": [

11 "bin",

12 "dist",

13 "defaults.json",

14 "defaults.example.json",

15 "README.md",

16 "SETUP.md",

17 "WORKFLOW.md"

18 ],

19 "scripts": {

20 "build": "tsc -p tsconfig.json",

21 "prepack": "npm run build",

22 "postinstall": "node ./dist/cli/postinstall.js",

High

Install Time Lifecycle Scripts

Package defines install-time lifecycle scripts.

package.jsonView on unpkg · L22

Medium

Ambiguous Install Lifecycle Script

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

package.jsonView on unpkg · L22

23 "typecheck": "tsc --noEmit -p tsconfig.json",

24 "proxy": "node --import tsx src/index.ts proxy",

25 "mcp": "node --import tsx src/index.ts mcp",

26 "mock": "node --import tsx src/index.ts mock-upstream",

27 "bench": "node --import tsx src/index.ts bench",

28 "collector": "node --import tsx src/index.ts collector",

29 "setup": "node --import tsx src/index.ts setup",

30 "scenario": "node --import tsx src/index.ts scenario",

31 "mcp-smoke": "node --import tsx src/index.ts mcp-smoke",

32 "serve": "npm run build && node dist/index.js collector"

33 },

34 "engines": {

35 "node": ">=20"

36 },

37 "keywords": [

38 "mcp",

39 "llm",

40 "interceptor",

41 "observability",

42 "claude-code",

dist/cli/setup.jsView file

Lines 1-21javascript

1import { mkdir, readFile, writeFile, access } from 'node:fs/promises';

2import { homedir } from 'node:os';

Critical

Ai Agent Control Hijack

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

dist/cli/setup.jsView on unpkg · L1

3import { dirname, join } from 'node:path';

dist/mcp/server.jsView file

•matchType = normalized_sha256 matchedPackage = llm-interceptor@0.3.3 matchedPath = dist/mcp/server.js matchedIdentity = npm:bGxtLWludGVyY2VwdG9y:0.3.3 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.

dist/mcp/server.jsView on unpkg

dist/self-update.jsView file

•matchType = normalized_sha256 matchedPackage = llm-interceptor@0.3.3 matchedPath = dist/self-update.js matchedIdentity = npm:bGxtLWludGVyY2VwdG9y:0.3.3 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.

dist/self-update.jsView on unpkg

dist/dev/mcp-smoke.jsView file

•matchType = normalized_sha256 matchedPackage = llm-interceptor@0.3.3 matchedPath = dist/dev/mcp-smoke.js matchedIdentity = npm:bGxtLWludGVyY2VwdG9y:0.3.3 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.

dist/dev/mcp-smoke.jsView on unpkg