CONSOLE WARNING: Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/. CONSOLE ERROR: XMLHttpRequest cannot load http://127.0.0.1:8000/xmlhttprequest/resources/access-control-sandboxed-iframe-denied.cgi. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access. This test verifies that sandboxed iframe does not have XmlHttpRequest access to its server. It will print "PASS" on success. -------- Frame: '-->' -------- PASS: Exception thrown. Sandboxed iframe XHR access was denied in 'send'. [Failed to execute 'send' on 'XMLHttpRequest': Failed to load 'http://127.0.0.1:8000/xmlhttprequest/resources/access-control-sandboxed-iframe-denied.cgi'.].