Document the security process (#8633)

* Document the security process

Closes: #8553

* Update SECURITY.md

Co-authored-by: Daniel Hofstetter <daniel.hofstetter@42dh.com>

* Update SECURITY.md

Co-authored-by: Daniel Hofstetter <daniel.hofstetter@42dh.com>

---------

Co-authored-by: Daniel Hofstetter <daniel.hofstetter@42dh.com>

Author: sylvestre

SECURITY.md

@@ -0,0 +1,44 @@
+# Security Policy
+
+## Supported Versions
+
+We provide security updates only for the latest released version of `uutils/coreutils`.
+Older versions may not receive patches.
+If you are using a version packaged by your Linux distribution, please check with your distribution maintainers for their update policy.
+
+---
+
+## Reporting a Vulnerability
+
+**Do not open public GitHub issues for security vulnerabilities.**
+This prevents accidental disclosure before a fix is available.
+
+Instead, please use the following method:
+
+- **Email:** [sylvestre@debian.org](mailto:Sylvestre@debian.org)
+- **Encryption (optional):** You may encrypt your report using our PGP key:
+Fingerprint: B60D B599 4D39 BEC4 D1A9 5CCF 7E65 28DA 752F 1BE1
+---
+
+### What to Include in Your Report
+
+To help us investigate and resolve the issue quickly, please include as much detail as possible:
+
+- **Type of issue:** e.g. privilege escalation, information disclosure.
+- **Location in the source:** file path, commit hash, branch, or tag.
+- **Steps to reproduce:** exact commands, test cases, or scripts.
+- **Special configuration:** any flags, environment variables, or system setup required.
+- **Affected systems:** OS/distribution and version(s) where the issue occurs.
+- **Impact:** your assessment of the potential severity (DoS, RCE, data leak, etc.).
+
+---
+
+## Disclosure Policy
+
+We follow a **Coordinated Vulnerability Disclosure (CVD)** process:
+
+1. We will acknowledge receipt of your report within **10 days**.
+2. We will investigate, reproduce, and assess the issue.
+3. We will provide a timeline for developing and releasing a fix.
+4. Once a fix is available, we will publish a GitHub Security Advisory.
+5. You will be credited in the advisory unless you request anonymity.