docs: add SECURITY.md with supported versions and reporting policy (#83)

Author: maskedsyntax

SECURITY.md

@@ -0,0 +1,48 @@
+# Security Policy
+
+## Supported Versions
+
+hashprep is currently in beta (`0.1.0bX`). Only the latest beta release on the `main` branch receives security updates. Older pre-releases are not patched — please upgrade to the newest version to pick up fixes.
+
+| Version    | Supported          |
+| ---------- | ------------------ |
+| `0.1.0b3`  | :white_check_mark: |
+| `< 0.1.0b3`| :x:                |
+
+Once hashprep reaches a stable `0.1.0` release, this table will be updated to reflect supported minor versions.
+
+## Reporting a Vulnerability
+
+If you believe you have found a security vulnerability in hashprep (the Python package, the CLI, or the documentation website under `web/`), **please do not open a public GitHub issue**.
+
+Instead, report it privately through one of the following channels:
+
+- **GitHub Private Vulnerability Reporting** — preferred. Open a report at <https://github.com/cachevector/hashprep/security/advisories/new>.
+- **Email** — `aftaab@aftaab.xyz` with the subject line `hashprep security report`.
+
+Please include as much of the following as you can:
+
+- A clear description of the issue and its impact.
+- The affected version(s) and component (library, CLI, website).
+- Steps to reproduce, a proof of concept, or a minimal failing example.
+- Any known mitigations or workarounds.
+
+### What to expect
+
+- **Acknowledgement:** within 72 hours of your report.
+- **Initial assessment:** within 7 days, including whether the report is accepted, needs more information, or is declined (with reasoning).
+- **Fix and disclosure:** for accepted reports, we will work on a fix, prepare a patched release, and coordinate a disclosure timeline with you. Reporters will be credited in the advisory unless they prefer to remain anonymous.
+
+### Scope
+
+In scope:
+
+- The `hashprep` Python package and CLI.
+- The documentation site in `web/`.
+- Build, packaging, and release tooling in this repository.
+
+Out of scope:
+
+- Vulnerabilities in third-party dependencies — please report those upstream. If a dependency issue affects hashprep users, we still appreciate a heads-up so we can bump the pinned version.
+- Issues that require physical access to a user's machine or already-compromised environments.
+- Denial of service caused by passing intentionally malformed datasets far outside the documented usage (e.g., multi-TB crafted inputs on a laptop).