diff --git a/zundler/assets/inject.js b/zundler/assets/inject.js
index 39ae6a3..d203d41 100644
--- a/zundler/assets/inject.js
+++ b/zundler/assets/inject.js
@@ -91,6 +91,10 @@ var fix_link = function(a) {
         a.addEventListener('click', virtual_click);
     } else if (a.getAttribute('href').startsWith('#')) {
         a.setAttribute('href', "about:srcdoc" + a.getAttribute('href'))
+    } else {
+        // External links should open in a new tab. Browsers block links to
+        // sites of different origin within an iframe for security reasons.
+        a.setAttribute('target', "_blank");
     }
 };