Add sandbox attribute to the secureiframe

www/common/sframe-common-file.js

@@ -517,6 +517,7 @@ define([
                         if (!thumb64) { return; }
                         thumb = thumb64;
                     }));
+                    if (file.type === "application/pdf") { return; }
                     MT.preview(buffer, {
                         type: file.type,
                     }, void 0, w(function (err, el) {

www/secureiframe/main.js

@@ -28,7 +28,7 @@ define([
             };
             window.rc = requireConfig;
             window.apiconf = ApiConfig;
-            $('#sbox-secure-iframe').attr('src',
+            $('#sbox-secure-iframe').attr('sandbox', 'allow-scripts allow-popups allow-modals').attr('src',
                 ApiConfig.httpSafeOrigin + '/secureiframe/inner.html?' + requireConfig.urlArgs +
                     '#' + encodeURIComponent(JSON.stringify(req)));