diff --git a/playground/voyage-playground.html b/playground/voyage-playground.html
index 376711c..250fdef 100644
--- a/playground/voyage-playground.html
+++ b/playground/voyage-playground.html
@@ -1248,6 +1248,13 @@ playground first-run shows a complete round-trip-able artifact.
         // v4.3 Step 25 — strip unsafe HTML-comments before markdown-it sees them.
         var safeText = stripUnsafeComments(text || '');
         var bodyHtml = md.render(safeText);
+        // v4.3 Step 1 — defense in depth: sanitize bodyHtml via DOMPurify
+        // (finding 1d3591d4). Applied to bodyHtml ONLY — fmHtml uses our
+        // own escapeHtml() on capturedFrontmatter and intentional
+        // <details>/<summary> markup that DOMPurify would otherwise strip.
+        var safeBody = (typeof window !== 'undefined' && window.DOMPurify && typeof window.DOMPurify.sanitize === 'function')
+          ? window.DOMPurify.sanitize(bodyHtml, { USE_PROFILES: { html: true } })
+          : escapeHtml(bodyHtml);
         // Pre-render-then-wrap for <details>: prepend a folded frontmatter
         // <details> block at the top if the front-matter plugin captured one.
         var fmHtml = '';
@@ -1255,7 +1262,7 @@ playground first-run shows a complete round-trip-able artifact.
           fmHtml = '<details><summary>Frontmatter</summary><pre><code>' +
             escapeHtml(capturedFrontmatter) + '</code></pre></details>';
         }
-        return fmHtml + bodyHtml;
+        return fmHtml + safeBody;
       }
 
       function escapeHtml(s) {
diff --git a/tests/playground/voyage-playground.test.mjs b/tests/playground/voyage-playground.test.mjs
index 7506f0d..e815aad 100644
--- a/tests/playground/voyage-playground.test.mjs
+++ b/tests/playground/voyage-playground.test.mjs
@@ -483,6 +483,22 @@ test('voyage-playground.html renderArtifact strips comments before md.render (v4
   assert.ok(stripIdx > 0 && stripIdx < renderIdx, 'stripUnsafeComments must run before md.render');
 });
 
+// v4.3 Step 1 — SC24-security defense in depth: renderArtifact bodyHtml is
+// sanitized via DOMPurify before DOM injection (finding 1d3591d4).
+test('voyage-playground.html renderArtifact sanitizes bodyHtml via DOMPurify (v4.3 Step 1, finding 1d3591d4)', () => {
+  const text = readFileSync(HTML, 'utf-8');
+  // The literal DOMPurify.sanitize(bodyHtml expression must be present.
+  assert.match(text, /DOMPurify\.sanitize\(bodyHtml/, 'DOMPurify.sanitize(bodyHtml call required in renderArtifact');
+  // USE_PROFILES: { html: true } must appear nearby (within the renderArtifact body)
+  const bodyStart = text.indexOf('function renderArtifact');
+  assert.ok(bodyStart > 0, 'renderArtifact() must exist');
+  const bodyEnd = text.indexOf('\n      }', bodyStart);
+  const body = text.slice(bodyStart, bodyEnd + 1);
+  assert.match(body, /USE_PROFILES:\s*\{\s*html:\s*true\s*\}/, 'USE_PROFILES html:true profile required inside renderArtifact');
+  // Return must reference safeBody, not raw bodyHtml
+  assert.match(body, /return\s+fmHtml\s*\+\s*safeBody/, 'renderArtifact return must use safeBody');
+});
+
 // v4.3 Step 26 — path-traversal + symlink/dotfile filter.
 test('voyage-playground.html declares isProjectPathSafe filter (v4.3 Step 26)', () => {
   const text = readFileSync(HTML, 'utf-8');