CHAT FILTERING, CONTENT MODERATION FAILURES & ASSET EVASION

Classification: Platform Security & Technical Vulnerability Investigation
Subject: Two Hat / CommunitySift Integration, The "Hashtag Plague" (#), Unicode & Homoglyph Evasion, Steganographic 2D/3D Asset Exploits, and Spatial Voice Loopholes
Year: 2026

1. Architecture of the Chat Filtering Engine

Roblox processes tens of billions of text strings monthly across in-game chat, spatial bubbles, and private messages. To handle this volume at sub-100ms latencies, Roblox combines rule engines, third-party acquisitions, and machine learning classifiers:

                         [ INCOMING CLIENT CHAT STRING ]
                                       │
                                       ▼
                     [ Stage 0: Pre-Processing & Sanitization ]
                     • UTF-8 byte normalization (NFKD/NFC)
                     • Whitespace & control character stripping
                                       │
                                       ▼
                     [ Stage 1: Fast-Path Regex & Trie Dictionaries ]
                     • In-memory Aho-Corasick trie matching
                     • Hardcoded static blacklist / allowlists
                                       │
                                       ▼
                     [ Stage 2: Two Hat / CommunitySift ]
                     • Acquired Sept 2021 (Two Hat Security)
                     • Contextual threat categories (0 to 6 risk scale)
                                       │
                                       ▼
                     [ Stage 3: In-House NLP & Transformer Layer ]
                     • DistilBERT / RoBERTa-based intent models
                                       │
                                       ▼
                     [ Stage 4: Session-Based Scoring Matrix ]
                     • Sliding-window cumulative risk accumulator
                                       │
                                       ▼
                     [ Stage 5: Output Generation ]
                     • Score >= Threshold: Mask with `###`
                     • Score < Threshold: Forward clear text

2. The "Hashtag Plague" (#): Causes of Severe False Positives

1. The Scunthorpe Problem & Substring Over-Matching: Basic innocent words like "basement", "circumstance", or "wristwatch" trigger full sentence masking due to crude substring blacklists.
2. Aggressive Under-13 PII Number Censorship: Any numeric sequence (e.g., "I have 5 coins", "Wait 2 minutes") is treated as a potential phone number or address by COPPA regex filters, rendering normal gameplay chat into * * * * * or ###.
3. Morphological Blindspots in Non-English Languages: Agglutinative languages (Tagalog, Indonesian, Turkish, German) attach prefixes and suffixes dynamically. Because tokenizers fail to recognize these compounds, entire legitimate sentences are replaced with #.

3. Predator Bypass Mechanics: Exact Technical Vectors

While ordinary children are heavily censored by the "Hashtag Plague," bad actors systematically bypass filters using well-documented Unicode, encoding, and orthographic evasion vectors:

┌──────────────────────────────────────────────────────────────────────────────────┐
│                          PREDATOR BYPASS TAXONOMY                                │
├──────────────────────────────────────────────────────────────────────────────────┤
│ 1. Invisible Unicode Insertion (Zero-Width Sequences)                            │
│ 2. Cyrillic / Greek Homoglyph Substitution (UTF-8 Visual Clones)                 │
│ 3. Combining Diacritical Marks & Grapheme Clustering                              │
│ 4. Lexical Decomposition & Multi-Message Phonetic Splitting                      │
│ 5. Steganographic Social Anchoring (Discord / Telegram Evasions)                  │
└──────────────────────────────────────────────────────────────────────────────────┘

• Invisible Zero-Width Characters: Inserting zero-width code points (\u200B Zero-Width Space, \u200C Non-Joiner, \uFEFF Byte Order Mark) inside banned keywords (e.g., d\u200Bi\u200Bs\u200Bc\u200Bo\u200Br\u200Bd). Regex keyword engines fail to match, while the game client discards zero-width glyphs, displaying a seamless "discord" on screen.
• Cyrillic & Greek Homoglyphs: Swapping Latin characters with visually identical Cyrillic code points (e.g., Latin a U+0061 vs Cyrillic а U+0430, Latin e vs Cyrillic е U+0435).
• Phonetic Off-Ramping: Obfuscated phrases to redirect children off-platform: "d!zc0rd", "d.i.s.c.", "the purple app", "pin: [digits]".

4. Asset Moderation Bypasses: 2D Clothing, Audio, & 3D Meshes

A. 2D Clothing Steganography & Multi-Part Stitching

• Alpha Channel Exploit: Setting sensitive pixels with pure white RGB (#FFFFFF) and low alpha ($A \approx 0.05$). The asset thumbnail appears completely blank during 3-second BPO web portal reviews, but renders fully visible when applied over dark avatar bodies in-game.
• Multi-Part Composite Stitching: Slicing explicit or hate imagery across three separate items (Shirt, Pants, T-Shirt Decal). Each asset passes isolated moderation, but composites into prohibited content when equipped together.

B. Audio Frequency Warping & Runtime Inversion

• Pitch-shifting audio by $\pm 7\text{--}15$ semitones breaks automated acoustic fingerprint hashes (Chromaprint).
• Uploading reversed audio that is played forward at runtime by setting Sound.PlaybackSpeed = -1 in Luau.

C. 3D Meshes & "Condo Games" via Runtime CSG

• Uploading harmless primitive shapes (cubes, spheres) that bypass static 3D upload scanning.
• At runtime, Luau scripts execute Part:SubtractAsync() and Part:UnionAsync() (Constructive Solid Geometry) to programmatically carve out explicit 3D anatomy and strip-club environments in memory.

5. Spatial Voice Chat Vulnerabilities

• Zero Proactive Moderation: Spatial voice operates over low-latency WebRTC Opus audio streams without inline real-time machine learning transcription.
• Buffer Overwriting: Client-side 30–60 second local ring buffers are overwritten if predators space out inappropriate comments, preventing victims from capturing evidence before submitting reports.