diff --git a/studio/frontend/src/components/assistant-ui/__tests__/html-svg-renderer.test.tsx b/studio/frontend/src/components/assistant-ui/__tests__/html-svg-renderer.test.tsx
index a1463ed9d2..2b13345ed2 100644
--- a/studio/frontend/src/components/assistant-ui/__tests__/html-svg-renderer.test.tsx
+++ b/studio/frontend/src/components/assistant-ui/__tests__/html-svg-renderer.test.tsx
@@ -26,17 +26,19 @@ describe("HtmlSvgRenderer", () => {
     ) as HTMLIFrameElement;
     expect(iframe.tagName).toBe("IFRAME");
     // SECURITY: allow-scripts + allow-modals leave script / alert /
-    // confirm operative IF the inherited host CSP ever permits inline;
-    // allow-popups + allow-popups-to-escape-sandbox so a `<base
-    // target="_blank">` link does not silently no-op; NEVER
-    // allow-same-origin or allow-top-navigation -- those would let
-    // the preview read parent.document and exfiltrate session data.
+    // confirm operative if the inherited host CSP ever permits inline.
+    // allow-popups lets ``<base target="_blank">`` links open without
+    // being silently dropped, BUT the popups INHERIT the sandbox
+    // (allow-popups-to-escape-sandbox is intentionally absent) so a
+    // tab opened from a malicious assistant link cannot use
+    // window.opener.top.location.* to tabnab the Studio tab.
+    // allow-same-origin and allow-top-navigation are NEVER granted.
     const sandbox = iframe.getAttribute("sandbox") ?? "";
     const sandboxTokens = sandbox.split(/\s+/);
     expect(sandboxTokens).toContain("allow-scripts");
     expect(sandboxTokens).toContain("allow-modals");
     expect(sandboxTokens).toContain("allow-popups");
-    expect(sandboxTokens).toContain("allow-popups-to-escape-sandbox");
+    expect(sandboxTokens).not.toContain("allow-popups-to-escape-sandbox");
     expect(sandbox).not.toContain("allow-same-origin");
     expect(sandbox).not.toContain("allow-top-navigation");
     // srcdoc carries the assistant HTML plus a defense-in-depth meta
diff --git a/studio/frontend/src/components/assistant-ui/html-svg-renderer.tsx b/studio/frontend/src/components/assistant-ui/html-svg-renderer.tsx
index c0fb3465ad..d257ab9756 100644
--- a/studio/frontend/src/components/assistant-ui/html-svg-renderer.tsx
+++ b/studio/frontend/src/components/assistant-ui/html-svg-renderer.tsx
@@ -356,13 +356,18 @@ function HtmlPreview({
       //                           that includes 'unsafe-inline'
       //   allow-modals         -- alert/confirm/prompt are not no-ops
       //                           when scripts do fire
-      //   allow-popups +       -- a ``<base target="_blank">`` link
-      //   allow-popups-to-        opens a regular browser tab rather
-      //   escape-sandbox          than an opaque-origin sandboxed one
-      // We do NOT grant allow-same-origin or allow-top-navigation, so
-      // the iframe cannot read parent.document, navigate the host
-      // page, or escape its origin.
-      sandbox="allow-scripts allow-modals allow-popups allow-popups-to-escape-sandbox"
+      //   allow-popups         -- the ``<base target="_blank">`` link
+      //                           rule can open a new tab instead of
+      //                           silently dropping the click
+      // We do NOT grant:
+      //   allow-same-origin / allow-top-navigation -- the iframe
+      //     cannot read parent.document or navigate the host page
+      //   allow-popups-to-escape-sandbox -- popups INHERIT the sandbox
+      //     so an opened tab cannot use ``window.opener.top.location``
+      //     to tabnab the Studio tab. The opened tab loads with an
+      //     opaque origin (some sites will render degraded) which is
+      //     the deliberate trade-off for tabnabbing safety.
+      sandbox="allow-scripts allow-modals allow-popups"
       style={{
         width: "100%",
         height: iframeHeight,