This project is an unofficial Proton Mail client. It handles credentials, OpenPGP private keys, and plaintext message bodies, so security reports are taken seriously.

Do not open a public issue for security problems.

Report privately via GitHub's private vulnerability reporting, or by email to filippofinke@protonmail.ch.

Please include a description, affected version/commit, and reproduction steps. You will get an acknowledgement within a reasonable timeframe and an update once the issue is assessed.

In scope: anything that could expose credentials, private keys, decrypted plaintext, or session tokens; signature-verification bypasses; weakening of the SRP/OpenPGP handling.

Out of scope: issues in upstream dependencies (proton-crypto, proton-srp, rustls, …) — report those upstream — and the Proton API itself.

• The mailbox password is never written to disk in cleartext. The unlocking key passphrase and auth tokens are stored in the OS keychain; only non-secret session metadata is written to disk (mode 0600).
• Address-key token signatures are verified on unlock; the SRP server proof and the signed modulus are verified on login.
• Verbose logs are designed to exclude secrets and plaintext. If you find a log line that leaks either, that is a vulnerability — please report it.

This software is provided "as is", without warranty (see LICENSE). Use at your own risk.