If you discover a security issue in SyncFlow, please report it privately:

• Use GitHub → Security → Report a vulnerability (private advisory) on this repository. Maintainers are notified immediately and the report stays hidden until a fix ships.
• For non-sensitive bugs (crashes, UI issues), a normal GitHub issue is fine.

Please include: affected version/OS, reproduction steps, and impact.

• E2E encryption on the wire: AES-256-GCM, Ed25519 signatures, X25519 key exchange, trust-on-first-use pinning, per-chunk SHA-256 chaining.
• Local-only control plane: the WebSocket bridge (port 18973) binds 127.0.0.1 only and enforces a browser origin allowlist.
• No telemetry: SyncFlow makes no internet connections. All traffic is LAN-local between paired devices.

• There is no TLS layer and no WAN relay — transport is a direct LAN TCP connection protected by application-layer E2E encryption.

• Peers are trust-on-first-use: verify the device pairing out-of-band if you face an active MITM on your network.

• LAN mode (SYNCFLOW_WS_HOST) is opt-in. The control plane binds loopback-only by default. When enabled, remote clients must exchange a single-use, 5-minute pairing code issued on the desktop for a bearer token (5 wrong attempts = 5-minute lockout); unauthenticated sockets can only run the pairing/auth handshake. Tokens are stored hashed in an owner-only pairing.json. Phase 0 of the mobile plan — covered by the t_lan_auth suite (27 checks).

The latest audit — findings, attack journal, seals and residual risks — is in docs/security-audit.md. The full threat model, hardening notes and 152-check security test evidence are in SECURITY_REPORT.md. The wire protocol (transports, pairing/auth, message catalogue, crypto profile, error catalogue, versioning policy) is specified in docs/protocol.md.

Only the latest release receives fixes. Older builds may be affected — please upgrade before reporting an issue present in a current release.