pdf.mustache in onebox-1.9.27.2

- old
+ new

@@ -1,4 +1,4 @@
-<a href='{{link}}' target="_blank"><span class='pdf-onebox-logo'></span></a>
-<h3><a href='{{link}}' target="_blank">{{title}}</a></h3>
+<a href='{{link}}' target="_blank" rel="noopener"><span class='pdf-onebox-logo'></span></a>
+<h3><a href='{{link}}' target="_blank" rel="noopener">{{title}}</a></h3>
 
 {{#filesize}}<p class='filesize'>{{filesize}}</p>{{/filesize}}