This repository is an engineering starter, not a compliance certification. Perform threat modeling, penetration testing and privacy review before production use.

• Argon2 password hashing
• Password complexity validation
• Email verification
• Account lockout after repeated failures
• Short-lived JWT access tokens
• Rotating refresh tokens with family reuse detection
• MFA using TOTP and one-time backup codes
• Session/device revocation
• Scoped API keys stored as hashes
• RBAC and resource-level membership checks
• Organization membership isolation
• Request IDs and security audit logs
• CORS and trusted-host controls
• Rate limiting with Redis or local fallback
• Message ownership and moderator authorization
• Attachment ownership and checksum checks
• Upload size limits
• Soft deletion for messages
• User blocking and moderation reports
• Secrets encrypted at rest for MFA configuration

• Set long random SECRET_KEY and ENCRYPTION_SECRET values using a secrets manager.
• Set ENVIRONMENT=production, DEBUG=false and EXPOSE_DEBUG_TOKENS=false.
• Use TLS for HTTP, WebSocket, PostgreSQL, Redis and object storage.
• Use secure, HTTP-only cookies for browser refresh tokens or a hardened token vault.
• Restrict CORS_ORIGINS and TRUSTED_HOSTS.
• Add CSP at the frontend/reverse proxy.
• Replace local file serving with private object storage and short-lived signed download URLs.
• Scan every upload for malware and prohibited content before status becomes ready.
• Add MIME inspection; never trust only the client-provided MIME type.
• Add content moderation appropriate to the product and jurisdiction.
• Add database backups, point-in-time recovery and Redis high availability.
• Alert on refresh-token reuse, login lockouts, privilege changes, report spikes and outbox failures.
• Define retention and deletion policies for messages, attachments, audit events and backups.
• Review lawful-access, encryption and data-residency requirements.

• Access tokens are validated during the handshake.
• Membership is rechecked for room subscriptions and domain events.
• Event payload size is limited.
• Unknown event types and invalid data produce structured errors.
• A reverse proxy should enforce connection, request and bandwidth limits.
• Clients should refresh access tokens before reconnecting rather than keeping long-lived tokens.

Do not open public issues for exploitable vulnerabilities. Report them privately to the repository owner with reproduction steps and impact.