Mostro App is a non-custodial client that handles private keys, Lightning payments, and end-to-end encrypted messages. Security reports are taken seriously and are handled through coordinated disclosure.

Do not open a public issue, pull request, or discussion for a security vulnerability.

Report it privately by email to security@mostro.network.

If you would like to encrypt your report, ask for a public key at that address before sending details.

The more of this you can provide, the faster the issue can be triaged:

• A description of the vulnerability and its impact (what an attacker can achieve).
• Steps to reproduce, or a proof of concept.
• Affected platform (Android, iOS, Web, macOS, Windows, Linux) and app version or commit hash.
• Affected layer, if known: Flutter UI (lib/) or Rust core (rust/).
• Any relevant logs, with keys, mnemonics, and invoices redacted.

Please do not test against other users, live trades, or third-party relays and Mostro nodes you do not operate. Use your own instance or testnet where possible.

• Acknowledgement: within 72 hours of the report.
• Initial assessment: severity and affected versions confirmed, normally within 7 days.
• Fix: critical issues are targeted for a fix within 30 days. Lower-severity issues are scheduled into the normal release cycle.
• Updates: you will be kept informed of progress until the issue is resolved.
• Disclosure: details are published only after a fix is available. Reporters are credited when the fix is announced, unless they ask to remain anonymous.

Security fixes are applied to the latest released version and to the main branch. Older releases do not receive backports; the web client at https://mostro.network/app/ always serves the latest build of main.

In scope — this repository, the Mostro client:

• The Rust core (rust/): Nostr protocol handling, cryptography, key derivation and storage, relay I/O, the Mostro state machine, Nostr Wallet Connect, and the offline message queue.
• The Flutter shell (lib/): UI, navigation, local state, and device/OS integration.
• Build and release tooling in this repository (scripts/, .github/workflows/), including the web bundle and its cross-origin isolation setup.

Out of scope — report these to their own projects:

• The Mostro daemon and its escrow logic: MostroP2P/mostro.
• Protocol types and the state machine shared with other clients: mostro-core.
• Third-party Nostr relays, Lightning wallets and NWC providers, and Mostro nodes operated by others.
• Upstream dependencies (nostr-sdk, Flutter, Rust crates) — report those upstream, though a heads-up is welcome if this app is exploitable through them.

The following are generally not treated as vulnerabilities:

• Automated scanner output with no demonstrated impact.
• Attacks that require a compromised, rooted, or jailbroken device, or physical access to an unlocked device.
• Social engineering, phishing, or a user voluntarily disclosing their seed phrase.
• Denial of service against public relays or a third party's infrastructure.
• Inherent properties of the Mostro protocol itself, such as a counterparty behaving dishonestly during a trade. Those are protocol design discussions, not client bugs.

A summary of the client's security properties — device-held keys, per-trade key derivation, and end-to-end encrypted messaging — is in the Security section of the README. Architectural details, including which logic belongs to the Rust core, are in AGENTS.md and .specify/ARCHITECTURE.md.

Your BIP-39 seed phrase is the only way to recover your identity and trade history. Nobody from the Mostro project will ever ask for it, for a private key, or for a Nostr Wallet Connect connection string. Any such request is an attempt to steal your funds.