Evaluator

Catch the cleartext the moment obfuscated JavaScript unpacks in a real browser.

Evaluator drives Chromium, hooks a JS function you choose (window.eval, String.fromCharCode, JSON.stringify, …), and prints the arguments that pass through that hook — often the deobfuscated payload Magecart-style skimmers hide until runtime.

compromised / demo page
        │
        ▼
  obfuscated JS  ──packs──▶  window.eval(cleartext)
        │                              │
        │                              ▼
        │                    evaluator hook + optional filter
        │                    (-s / --regex / --rules)
        ▼
   screenshots + payloads you can read

You get	It solves
Live web UI + screenshot stream	“What did this page actually `eval`?”
Rust CLI (spawns Node evaluate/batch)	Batch / interactive hunts without guessing at packed source
Rust MCP tools for agents	Same evaluate path from Cursor / automation
Local demo fixtures + Willem rules	Reproduce the VB2021 story on localhost before you touch live shops

Live: https://evaluator.interchouette.net

Docs

Doc	Description
`CHANGELOG.md`	Release notes
`evaluator/MAGECART.md`	Magecart / Grelos product notes
`evaluator/README.md`	Rust CLI details
`docker/`	Dockerfile / Compose (Hub overview lives in private `.cursor/scripts/DOCKERHUB.md`)

Typically helps with deobfuscating patterns like this Stack Overflow case using String.fromCharCode, window.eval, or other functions like JSON.stringify.

The story (why this exists)

Static scanners (Willem’s rules, VT + YARA) see files on disk. Skimmers often stay opaque until the browser runs them. Evaluator is the complementary runtime tool: after the packer calls eval, you see grelos_v, checkout, gate URLs, and friends in the hook output.

Full product notes (warnings, canary vs demos, batch): evaluator/MAGECART.md — start there for Magecart / Grelos context.

References

Jérôme Segura (Malwarebytes), Hunting web skimmers with VirusTotal and YARA, VB2021 — PDF
Product notes (Magecart / Grelos / Blogspot demo fixtures): evaluator/MAGECART.md
Astra — signs of hacked OpenCart / Magento / PrestaShop stores (malicious JS): getastra.com article
Willem de Groot — magento-malware-scanner frontend rules: rules/frontend.txt (local snapshot: evaluator/rules/frontend.txt)

Screenshots — web UI in action

Try it in 30 seconds

Canary (hook smoke test — W3Schools eval):

evaluator evaluate \
  --url 'https://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_eval' \
  --fn window.eval
# expect a payload like: x * y

Same idea in the browser (production gateway):

https://evaluator.interchouette.net/evaluate/?url=https://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_eval&function=window.eval

Demos — illustrate the PDF story on localhost

Research fixtures under evaluator/archive/fixtures/. Serve only on localhost. Do not expose them through Nest, Express, the Docker public image, or any internet-facing route. Details: DEOBFUSCATED.md, MAGECART.md.

#	Obfuscated	Deobfuscated	What you learn
1	`demo1shop.html`	`demo1shop.deobfuscated.js`	Neutral shop JS; historical `_0xd419` hex packer → `eval` → `checkout` / `cart`
2	`demo2grelos.html`	`demo2grelos.deobfuscated.js`	Grelos-shaped marker; light teaching packer
3	`demo3grelos.html`	`demo3grelos.deobfuscated.js`	Same marker; Magento-era `_0x` hex-table → `eval` (demo‑1 packing family)

cd rust/archive/fixtures && python3 -m http.server 8765
# or: ./smoke-demos.sh

evaluator evaluate --url http://127.0.0.1:8765/demo1shop.html --fn window.eval -s checkout,cart --excerpt
evaluator evaluate --url http://127.0.0.1:8765/demo2grelos.html --fn window.eval -s grelos_v --excerpt
evaluator evaluate --url http://127.0.0.1:8765/demo3grelos.html --fn window.eval -s grelos_v --excerpt

Filter live/batch hits with keywords, regex, or Willem’s rules:

evaluator batch -p rust/archive/All-Live-Magento-Sites.csv \
  -f window.eval -n 1 \
  --rules rust/rules/frontend.txt

Authorized research only. If you confirm a live compromise, report it responsibly to the merchant / hoster.

Architecture

Browser (Angular SPA)
    → Node serve :4000  (Express: static, WS evaluate, GET /evaluate)
        → Nest API :3333     (/api/functions)
        → Chromium via libs/util/puppeteer

Rust CLI / Rust MCP
    → spawn Node evaluate | batch  (same entry as serve; no :4000 required)

Image: interchouette/evaluator — web + Chromium + Rust CLI + Rust MCP.

Compose profile: web (ports 4000 + 9790).

Mode	Behavior
`web` / default	Nest + Node `serve` `:4000`; MCP HTTP sidecar if `ENABLE_MCP=1`
`ENABLE_MCP=0`	Web only
`mcp`	`evaluator-mcp` stdio
`mcp --http`	MCP HTTP only
`evaluator` / interactive	Rust prompt; spawn Node evaluate/batch
`evaluate` / `batch`	Rust → one Node child; no MCP sidecar

How the pieces fit the hunt:

Approach	What it sees	Strength
Willem frontend/backend rules	File / CMS / static JS	Fast signature match on disk
Segura VB2021 (VT + YARA)	Submitted HTML/JS corpus, gates	Hunt infrastructure at scale
Evaluator	Live hooked call arguments	Sees post-`eval` cleartext in a real browser

API — Quick Start

Use

evaluate/?url=[site url]&function=[function to evaluate]

Example (dev FE on port 4200)

http://localhost:4200/evaluate/?url=https://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_eval&function=window.eval

Example (production)

https://evaluator.interchouette.net/evaluate/?url=https://www.w3schools.com/jsref/tryit.asp?filename=tryjsref_eval&function=window.eval

Production / Docker Node gateway listens on port 4000. A screenshot of the website is included in the response stream.

Docker — pull, run, build, CI/CD

Images (primary):

Docker Hub: interchouette/evaluator (web + CLI + MCP; Playwright default, or USE_PUPPETEER=1)
GHCR: ghcr.io/interchouette-itc/evaluator
Personal GHCR (optional): ghcr.io/groussac/evaluator

The former Hub mirror gregoshop/evaluator is deprecated and is no longer published. No separate evaluator-base. MCP HTTP is on by default (ENABLE_MCP=0 to disable).

Run CI-built `:dev` (preferred locally)

make docker-pull-dev
make docker-run

Visit http://localhost:4000/

Build (CI / repro)

make docker-build-dev   # or make docker-build

Optional local packaging after cd www && npm run build: make docker-build.

CLI / MCP (built into the all-in-one image; CLI does not need web up):

# One-shot evaluate
make docker-run-cli ARGS='evaluate --url https://example.com --fn window.eval'
# CSV batch
make docker-run-cli ARGS='batch -p /data/archive/test.csv -n 1 -f window.eval'
# Interactive: docker run -it --rm --network host interchouette/evaluator:dev evaluator
make docker-run-mcp          # stdio (evaluator-mcp)
# MCP HTTP is published on :9790 with make docker-run (ENABLE_MCP=1)

CI / CD

Workflow	Trigger	What
`ci.yml`	PR / push to `dev`	`www/`: `npm ci` + `npm run build`
`docker-build-push-dev.yml`	manual	monolith `:dev` + `:latest` → Hub + GHCR; then Render via `RENDER_DEPLOY_HOOK` (Hub Overview: `python3 .cursor/scripts/sync-hub-description.py`)
`release.yml`	GitHub Release `vX.Y.Z`	attach host `evaluator` + `evaluator-mcp` binaries; push monolith `:X.Y.Z` + `:latest` → Hub + GHCR; Render redeploy

Secret RENDER_DEPLOY_HOOK = full Render Deploy Hook URL (repo secret, not an app env). Without it, Hub still updates; Render stays on the old digests until a manual redeploy.

To publish a release: bump both www/package.json and rust/Cargo.toml to the same X.Y.Z, tag vX.Y.Z, create the GitHub Release. Workflow validates the tag against both versions.

Development — host Node, build, test

Prerequisites

Node.js >=24 on the host (CI/Docker use Node 26; agents must not install another)
npm >=11
Docker web image: single node:26-trixie-slim multi-stage build with distro Chromium
Evaluate engine: Playwright by default on distro Chromium (PUPPETEER_EXECUTABLE_PATH); set USE_PUPPETEER=1 for Puppeteer

cd www && npm install

Development server

cd www && npm start

Dev UI: http://localhost:4200/ (API proxied; Nest backend on 3333).

Build

cd www && npm run build

Artifacts land in www/dist/. Serve production Node gateway + Nest:

cd www && npm run serve

Then open http://localhost:4000/

Test

cd www && npm test

Rust CLI — host, no Docker required

Same shape as sibling ITC crates (make build / make run / make install):

make build              # → rust/target/debug/evaluator (+ evaluator-mcp)
make install            # → ~/.cargo/bin (features apps)
make run ARGS='evaluate --url http://127.0.0.1:8765/demo1shop.html --fn window.eval'

Needs cd www && npm run build (Node entry at www/dist/evaluator/server/server.js) + Chromium.

Mode	Command
Interactive	`make run` or `evaluator`
One-shot	`evaluator evaluate --url … [--fn …]`
CSV batch	`evaluator batch -p archive/test.csv -f window.eval -n 1`

See evaluator/README.md for details.

MCP — agent tools + engine advice

Rust MCP (evaluator-mcp, rmcp): tools evaluate, list_functions, and batch (urls[] and/or local CSV path with a Domain column; max 50 URLs). Tools spawn the shared Node entry - no :4000 required. Large CSVs stay on the Rust CLI (evaluator batch -p …).

Prefer MCP HTTP over stdio (stdio pays a Docker spawn cost on cold start).

Endpoint	Auth	When
`http://127.0.0.1:9790/mcp`	none	Local sidecar (Docker `-p 9790:9790`)
`http://mcp:mcp@127.0.0.1:4000/mcp`	basic `MCP_USER`/`MCP_PWD` (defaults `mcp`/`mcp`)	Via Express proxy on the web port
`https://mcp:mcp@evaluator.interchouette.net/mcp`	same boat defaults	Public demo (Render: only web `PORT` is public; use `/mcp`, not `:9790`)

Defaults are public by design for the shared demo. Override MCP_USER/MCP_PWD only for a private deploy and share creds out-of-band — do not reuse DB_*. Set ENABLE_MCP_PROXY=0 to disable the gateway route.

Cursor HTTP example:

{ "url": "https://mcp:mcp@evaluator.interchouette.net/mcp" }

make run-mcp-http          # host: evaluator-mcp --http (:9790)
make run-mcp               # host: stdio
make docker-run-mcp        # image stdio

Engine and MCP advice (local bench)

Same page and hook: JSON.stringify on https://cursor.com. Warmup discarded; wall times to gateway /evaluate (what both MCP transports call). Stdio numbers below include a cold docker run --rm per call.

Combo	Median	Notes
MCP HTTP + Playwright	~9.5 s	Recommended default
MCP HTTP + Puppeteer	~11.3 s	Opt in with `USE_PUPPETEER=1`
MCP stdio + Playwright	~13.6 s	~+4 s Docker spawn vs HTTP
MCP stdio + Puppeteer	~15.6 s	Slowest of the four

Takeaways:

Prefer Playwright (default; unset or USE_PUPPETEER=0).
Prefer MCP HTTP over stdio when available — same evaluate work, no spawn tax. Local :9790 or proxied https://mcp:mcp@host/mcp.
Hit counts and screenshots were comparable across engines (~75–84 console hits).

License

GPL-3.0-or-later — see LICENSE.

Security

Errors

If you see typos or errors, open a pull request on the default working branch. Thanks.

Name		Name	Last commit message	Last commit date
.github		.github
.vscode		.vscode
docker		docker
docs		docs
rust		rust
www		www
.dockerignore		.dockerignore
.gitignore		.gitignore
LICENSE		LICENSE
Makefile		Makefile

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Demos — illustrate the PDF story on localhost

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Engine and MCP advice (local bench)

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