Postern is self-hosted software: Skyphusion Labs operates no mail service and holds no user mail; the only instance it runs is the public demo mailbox (see PRIVACY.md). This policy covers vulnerabilities in the Postern software, not incidents on any particular operator instance, which are the operator to handle. A vulnerability you find through the demo is a software vulnerability and belongs here.

Security fixes land on main and ship in the next release. Run a current release.

Please report privately, not in a public issue:

• Preferred: GitHub private vulnerability reporting on this repository (Security -> Report a vulnerability), which opens a private advisory thread.

Include the affected component (inbound/, relay/, mcp/, imap/, webmail/, clients/python/), a description, and reproduction steps if you have them. Please give us a reasonable window to fix and release before public disclosure. We will acknowledge your report and keep you updated on the fix.

In scope: the code in this repository. Out of scope: the configuration, secrets, DNS, and Cloudflare account of any operator running their own instance; those are the operator responsibility. If you are an operator with an incident on your own deployment, this project cannot access or act on data in an instance it does not run.

Two things are documented defaults, not vulnerabilities: a per-identity agent credential whose scopes include read reading mail addressed to every address on a deployment (README, "What an agent credential can read"), and the published demo token reading the whole demo mailbox (PRIVACY.md). A report is in scope where the software crosses a boundary it states: a credential changing mail outside its own bound address, or a webmail cookie session reading beyond its own person and role queues.