diff --git a/scripts/validate-case-studies.mjs b/scripts/validate-case-studies.mjs
index f94f1c09..1989f571 100644
--- a/scripts/validate-case-studies.mjs
+++ b/scripts/validate-case-studies.mjs
@@ -2,6 +2,34 @@
 import { readFileSync } from 'node:fs';
 import { reportAndExit } from './lib/validate-utils.mjs';
 
+// data/case-studies.json is regenerated from the cncf.io WordPress REST API by
+// scripts/collect-case-studies.mjs, which copies each post's `link` through
+// verbatim, and src/components/CaseStudies renders every one of them as an
+// <a href> under a CNCF organization name. A scheme prefix test is not a gate:
+// it accepts any host, and it accepts a userinfo component
+// ("https://www.cncf.io@evil.example/") that resolves to a hostile host while
+// reading as CNCF to a maintainer skimming a generated JSON diff. Parse the URL
+// and hold the host to an allow-list, the same standard
+// scripts/lib/profile-image.mjs already applies to profile images.
+const ALLOWED_HOST_SUFFIXES = ['cncf.io'];
+
+function publishableUrl(value) {
+  if (typeof value !== 'string') return null;
+  let url;
+  try {
+    url = new URL(value.trim());
+  } catch {
+    return null;
+  }
+  if (url.protocol !== 'https:') return null;
+  if (url.username || url.password) return null;
+  const host = url.hostname.toLowerCase();
+  const allowed = ALLOWED_HOST_SUFFIXES.some(
+    (domain) => host === domain || host.endsWith(`.${domain}`),
+  );
+  return allowed ? url : null;
+}
+
 const data = JSON.parse(
   readFileSync(new URL('../data/case-studies.json', import.meta.url)),
 );
@@ -13,11 +41,11 @@ if (Number.isNaN(Date.parse(data.generatedAt)))
     severity: 'error',
     message: 'generatedAt must be a parseable date',
   });
-if (!data.sourceUrl || !/^https:\/\//.test(data.sourceUrl))
+if (!data.sourceUrl || !publishableUrl(data.sourceUrl))
   errors.push({
     path: 'case-studies.json',
     severity: 'error',
-    message: 'sourceUrl must be an https URL',
+    message: `sourceUrl must be an https URL, with no userinfo, on ${ALLOWED_HOST_SUFFIXES.join(' or ')}`,
   });
 if (!Array.isArray(data.caseStudies) || !data.caseStudies.length)
   errors.push({
@@ -43,12 +71,18 @@ for (const entry of data.caseStudies || []) {
       severity: 'error',
       message: 'missing organization',
     });
-  if (!entry.url || !/^https:\/\//.test(entry.url) || urls.has(entry.url))
+  if (!entry.url || urls.has(entry.url))
     errors.push({
       path: String(id),
       severity: 'error',
       message: 'missing or duplicate url',
     });
+  else if (!publishableUrl(entry.url))
+    errors.push({
+      path: String(id),
+      severity: 'error',
+      message: `url must be an https URL, with no userinfo, on ${ALLOWED_HOST_SUFFIXES.join(' or ')}: ${JSON.stringify(entry.url)}`,
+    });
   urls.add(entry.url);
   if (!Array.isArray(entry.projects))
     errors.push({
diff --git a/tests/validate-case-studies.test.mjs b/tests/validate-case-studies.test.mjs
index 36b96a28..a6f5be4d 100644
--- a/tests/validate-case-studies.test.mjs
+++ b/tests/validate-case-studies.test.mjs
@@ -88,3 +88,93 @@ test('rejects an entry with a non-array projects field', () => {
   assert.equal(result.status, 1);
   assert.match(result.stderr, /projects must be an array/);
 });
+
+test('rejects a sourceUrl on a host outside cncf.io', () => {
+  const result = runScriptWithFixtures(
+    SCRIPT,
+    fixture({ ...validData, sourceUrl: 'https://evil.example/case-studies/' }),
+  );
+  assert.equal(result.status, 1);
+  assert.match(result.stderr, /sourceUrl must be an https URL/);
+});
+
+test('rejects a sourceUrl that spoofs cncf.io through a userinfo component', () => {
+  const result = runScriptWithFixtures(
+    SCRIPT,
+    fixture({
+      ...validData,
+      sourceUrl: 'https://www.cncf.io@evil.example/case-studies/',
+    }),
+  );
+  assert.equal(result.status, 1);
+  assert.match(result.stderr, /sourceUrl must be an https URL/);
+});
+
+test('rejects an entry url on a host outside cncf.io', () => {
+  const result = runScriptWithFixtures(
+    SCRIPT,
+    fixture({
+      ...validData,
+      caseStudies: [{ ...validEntry, url: 'https://evil.example/acme/' }],
+    }),
+  );
+  assert.equal(result.status, 1);
+  assert.match(result.stderr, /url must be an https URL/);
+});
+
+test('rejects an entry url that only prefixes an allowed host', () => {
+  const result = runScriptWithFixtures(
+    SCRIPT,
+    fixture({
+      ...validData,
+      caseStudies: [
+        { ...validEntry, url: 'https://www.cncf.io.evil.example/acme/' },
+      ],
+    }),
+  );
+  assert.equal(result.status, 1);
+  assert.match(result.stderr, /url must be an https URL/);
+});
+
+test('rejects an entry url that spoofs cncf.io through a userinfo component', () => {
+  const result = runScriptWithFixtures(
+    SCRIPT,
+    fixture({
+      ...validData,
+      caseStudies: [
+        {
+          ...validEntry,
+          url: 'https://www.cncf.io@evil.example/case-studies/acme/',
+        },
+      ],
+    }),
+  );
+  assert.equal(result.status, 1);
+  assert.match(result.stderr, /url must be an https URL/);
+});
+
+test('rejects a non-https entry url', () => {
+  const result = runScriptWithFixtures(
+    SCRIPT,
+    fixture({
+      ...validData,
+      caseStudies: [
+        { ...validEntry, url: 'http://www.cncf.io/case-studies/acme/' },
+      ],
+    }),
+  );
+  assert.equal(result.status, 1);
+  assert.match(result.stderr, /url must be an https URL/);
+});
+
+test('accepts an entry url on a cncf.io subdomain', () => {
+  const result = runScriptWithFixtures(
+    SCRIPT,
+    fixture({
+      ...validData,
+      caseStudies: [{ ...validEntry, url: 'https://cncf.io/case-studies/acme/' }],
+    }),
+  );
+  assert.equal(result.status, 0, result.stderr);
+  assert.match(result.stdout, /Validated 1 case studies/);
+});