diff --git a/.github/workflows/checks.yml b/.github/workflows/checks.yml
new file mode 100644
index 0000000..25cd65b
--- /dev/null
+++ b/.github/workflows/checks.yml
@@ -0,0 +1,26 @@
+name: Checks
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  security-policy:
+    name: Disclosure policy
+    runs-on: ubuntu-latest
+    steps:
+      # Pinned to a commit, not a tag, for the reason T59 gives: a tag moves and
+      # the reviewed build is not the published one. Same SHAs the initiative
+      # workflows already use.
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1
+      - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020
+        with:
+          node-version: 24
+      # This repository has no package.json and needs none — the check is one
+      # script against one file, and a dependency would be a supply chain for a
+      # thing that reads Markdown.
+      - run: node scripts/check-security-policy.mjs
diff --git a/SECURITY.md b/SECURITY.md
new file mode 100644
index 0000000..cb0de5e
--- /dev/null
+++ b/SECURITY.md
@@ -0,0 +1,48 @@
+# Reporting a security issue
+
+This is the organization-wide policy. It applies to every Morelitea repository
+that does not carry its own `SECURITY.md`.
+
+## How to report
+
+Email **security@morelitea.com**. Please do not open a public issue.
+
+Include what you can:
+
+- what the issue is, and where
+- how to reproduce it
+- what an attacker gets — the part that decides how fast we move
+- a suggested fix, if you have one
+
+## What to expect
+
+- Acknowledgement within 48 hours.
+- An estimated timeline once we have reproduced it.
+- Notice when it is resolved.
+- Credit in the release notes, unless you would rather stay anonymous.
+
+## Which repositories this covers
+
+GitHub applies this policy to every Morelitea repository that has no policy of
+its own. A repository-local `SECURITY.md` takes precedence and may provide a
+more specific reporting route or support window.
+
+Reports about any non-archived repository are supported. Reports about an
+archived repository are still welcome, but the resolution may be an archive
+notice rather than a patch.
+
+## What we ask
+
+- Give us a chance to fix it before disclosing publicly.
+- Do not access, change or keep data that is not yours while testing.
+- Do not run denial-of-service tests or automated scanners against our hosted
+  services. Test against your own deployment — everything under `initiative` is
+  self-hostable, which makes that straightforward.
+
+## Scope
+
+First-party code, our deployment configuration, and our CI workflows.
+
+Vulnerabilities in third-party dependencies are out of scope as issues in their
+own right, but we want to hear about a vulnerable transitive dependency reaching
+one of our releases — that is our problem to fix even when the bug is not ours.
diff --git a/scripts/check-security-policy.mjs b/scripts/check-security-policy.mjs
new file mode 100644
index 0000000..aedfd61
--- /dev/null
+++ b/scripts/check-security-policy.mjs
@@ -0,0 +1,46 @@
+/**
+ * The organization-wide disclosure policy has to stay usable.
+ *
+ * This file is what GitHub shows on every repository that has no policy of its
+ * own, so a broken link or a missing reporting route is broken everywhere at
+ * once and shows up nowhere — no build consumes it, and nothing else reads it.
+ *
+ * Checks the things that make it a policy rather than a page: somewhere to
+ * report, a promise about what happens next, and links that resolve.
+ */
+import {readFileSync} from 'node:fs';
+
+const text = readFileSync('SECURITY.md', 'utf8');
+const problems = [];
+
+// A reporting route. Without one the document is an essay.
+if (!/\b[\w.+-]+@[\w-]+\.[\w.-]+\b/.test(text) && !/security\/advisories\/new/.test(text)) {
+  problems.push('no reporting route: neither an email address nor a private advisory link');
+}
+
+// What a reporter is told to expect. The policy makes a commitment; if the
+// section naming it disappears, the commitment disappears silently.
+if (!/##\s*What to expect/i.test(text)) {
+  problems.push('no "What to expect" section — a reporter is told nothing about what follows');
+}
+
+// Scope. A policy without one invites testing nobody wants.
+if (!/##\s*Scope/i.test(text)) {
+  problems.push('no "Scope" section');
+}
+
+// Relative links must resolve. An absolute one is somebody else's uptime.
+for (const [, label, target] of text.matchAll(/\[([^\]]+)\]\(([^)]+)\)/g)) {
+  if (/^(https?:|mailto:|#)/.test(target)) continue;
+  try {
+    readFileSync(target.split('#')[0], 'utf8');
+  } catch {
+    problems.push(`link "${label}" points at ${target}, which is not in this repository`);
+  }
+}
+
+if (problems.length) {
+  console.error('SECURITY.md problems:\n' + problems.map((p) => `  - ${p}`).join('\n'));
+  process.exit(1);
+}
+console.log('SECURITY.md: reporting route, expectations, scope and links all present');