RXVM — Amazon Client-Side Bot Detection (Reverse Engineering POC)

Reverse engineering of Amazon's RXVM bytecode virtual machine and its client-side bot detection / behavioral telemetry system.

Files

File	Description
RXVM_Paper.pdf	Full academic research paper (12 pages, peer-review format)
A10_Report.pdf	Visual technical report — architecture diagrams, feature importance, model analysis
ANALYSIS.md	Full technical writeup — architecture, all 15 payloads, data flow
rxvm_disasm.py	RXVM bytecode disassembler (v4) — XOR key reseeding, closure discovery
rxc_decrypt.py	Amazon rxc= cookie decryptor — RC4 decryption, metric stream parsing
a10_model.py	A10 neural network reimplementation — inference, feature importance, simulation
a10_model_weights.json	Extracted model weights — norms, dense, batchnorm, all layers
extract_rx_runtime.py	Utility to extract rx.M matrix module from Amazon page HTML
rx_M_extracted.js	Deobfuscated rx.M source — confirmed pass-through, no weight rescaling
payload0_crypto_analysis.txt	Annotated disassembly of the crypto payload with JS equivalents
rxvm_crypto_layer_analysis.docx	Detailed crypto layer analysis document
rxvm_full_disasm.txt	Complete disassembly of all 15 payloads from a live Amazon page

Quick Start

Disassemble RXVM payloads from an Amazon page

python3 rxvm_disasm.py page.html

Disassemble a single base64 payload

python3 rxvm_disasm.py -b64 "UlgB..."

Decrypt an rxc cookie

python3 rxc_decrypt.py "AGVoY2hlY2..."

Analyze the neural network

python3 a10_model.py

Score a custom feature vector

python3 a10_model.py --score 450 500 60 300 310 45 80 90 40 18 48 3 \
    0.4 0.4 0.4 0.02 0.11 0.11 0.4 0.02 \
    160 160 520 520 240 240 620 620 100 120 7

Known Limitation: Neural Network Scoring

The A10 model reimplementation extracts the correct architecture, features, and weights, but all profiles currently score ~1.0. The Dense layer constructor in the bytecode passes weights through rx.M(), a matrix module in the RXVM core JS runtime (not the bytecode payloads). This module likely rescales the 8-bit minifloat weights at instantiation time. Without it, BatchNorm betas dominate the pre-sigmoid value, saturating the output.

To fix: extract rx.M from the RXVM interpreter's plaintext JavaScript on Amazon pages.

No External Dependencies

All tools are pure Python 3, standard library only. No pip installs required.

System Overview

Amazon Page HTML
    └── rx.ex64("base64...") × 15 payloads
         │
         ├── [0]  Crypto layer (AES-128-CBC + RC4 fallback)
         ├── [1]  Statistics library (sum, mean, stddev, float16 codec)
         ├── [2]  Cookie fingerprint (hash(UA + SID) → fnpb key)
         ├── [3]  State persistence (EMA tracking via encrypted localStorage)
         ├── [4]  Bot fingerprinting (Playwright, WebDriver, ChromeDriver,
         │        Puppeteer, PhantomJS, SwiftShader, headless dimension checks)
         ├── [5]  Mouse click timing (mousedown/mouseup duration)
         ├── [6]  Mouse movement (velocity + angular acceleration)
         ├── [7]  Scroll behavior (scroll velocity)
         ├── [8]  Navigation timing (visit count, session duration)
         ├── [9]  Viewport / screen dimensions
         ├── [10] ML runtime (Dense, BatchNorm, ReLU, Sigmoid layers)
         ├── [11] ML scoring (31→16→16→1 neural net, weights inline)
         ├── [12] Strong interaction detection (mouse/scroll threshold gate)
         ├── [13] Cookie action tracking (highest interaction tier)
         └── [14] AI agent detection (Perplexity browser agent regex scanning)

Responsible Disclosure

Responsibly disclosed to Amazon. Confirmed by Amazon.

Date	Event
Mar 12, 2026	Initial discovery during consumer research into A10 algorithm
Mar 14, 2026	Reverse engineering complete, all tools validated across multiple pages
Mar 14, 2026	Responsible disclosure submitted to Amazon Security
Mar 16, 2026	Confirmed by Amazon

About

Research by Nicholas Kloster (NuClide / ExileKingdom). Tools built collaboratively with Claude (Anthropic).

All analysis was performed on publicly-served JavaScript executing in the researcher's own browser. No exploitation, no circumvention, no access to Amazon's server-side systems.

License

MIT