The project is pre-1.0. Security fixes target the main branch.

Open a private report through GitHub security advisories if available. If not, open a minimal public issue that describes the affected area without sharing credentials, tokens, message bodies, or mailbox dumps.

• Do not use normal account passwords; use app passwords or authorization codes with IMAP enabled.
• Do not commit .env, cache directories, key files, or mailbox exports.
• CLI credentials must be supplied through environment variables.
• The optional TUI cached login (login.json) and the identity keypair (identity.json) are stored under SLIP_HOME/~/.slip with mode 0600 on Unix.
• SLIP_PASSPHRASE encrypts the identity secret key at rest with Argon2id + XChaCha20-Poly1305, so a stolen identity.json is useless without the passphrase. Set it before first run, or on a later run to migrate an existing plaintext key (clearing it migrates back). Slip has no recovery path: lose the passphrase and the identity — and any ciphertext only it can open — is unrecoverable.
• TLS certificate verification cannot be disabled by a runtime switch.
• Logging is off unless SLIP_LOG is set, and then records metadata only (addresses, message ids, sizes, counts) — never passwords, auth codes, keys, or message bodies. The account secret is additionally registered with the logger and masked to *** in every line as a backstop.

Slip messages are end-to-end encrypted with box-v1 (X25519 + XSalsa20-Poly1305 via the RustCrypto crypto_box crate) once both sides have seen each other's key — automatic after one round trip. Trust is TOFU: a changed sender key suspends encryption and warns until the user re-trusts it. Full format and threat model: docs/PROTOCOL.md.

Known limitations, by design of email as a transport:

• Metadata (addresses, timing, approximate sizes, the [slip/chat] subject) is visible to mail providers.
• First contact sends an empty public-key exchange, never user content. Unknown or changed keys block text and attachment sends (including retries). The TOFU window still allows an active provider-level MITM at first contact; compare fingerprints out of band before sensitive conversations.
• Web listens only on 127.0.0.1 with a per-process access token. It has no public hosting mode. Web credentials are held in memory, not persisted.
• Received chat is removed only after successful validation and local storage. Local history is plaintext; account directories use mode 0700 on Unix. Remote cleanup cannot guarantee deletion of provider backups or unrecognized copies.
• No forward secrecy yet: compromise of an identity key exposes archived past traffic. Ratcheting is on the roadmap.

Electron starts a loopback-only Rust backend on a random port with an ephemeral access token. Renderer Node.js is disabled; sandbox, context isolation and web security are enabled. External navigation, new windows and permission requests are denied. Mailbox credentials are not inherited from the shell and are kept only in the current backend session. Closing the app terminates the backend; local identity, history and attachments remain on the device. Distribution packages contain only app resources and the matching backend, never development account stores.