title: Error while parsing the 'sandbox' attribute: 'ms-allow-popups' is an invalid sandbox flag
body: <p>I want to make a very basic excel add-in. However I have got error after loading the xml file in <code>Excel Online</code>:</p>
  
  <p><a href="https://i.stack.imgur.com/54cmh.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/54cmh.png" alt="enter image description here"></a></p>
  
  <p>Does anyone know how to fix these errors?</p>
  
  <p>Here is the xml file:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;OfficeApp xmlns="http://schemas.microsoft.com/office/appforoffice/1.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:bt="http://schemas.microsoft.com/office/officeappbasictypes/1.0" xmlns:ov="http://schemas.microsoft.com/office/taskpaneappversionoverrides" xsi:type="TaskPaneApp"&gt;
    &lt;Id&gt;2145a915-4e7b-473f-a879-a5a5e8654152&lt;/Id&gt;
    &lt;Version&gt;1.0.0.0&lt;/Version&gt;
    &lt;ProviderName&gt;Microsoft&lt;/ProviderName&gt;
    &lt;DefaultLocale&gt;en-US&lt;/DefaultLocale&gt;
    &lt;DisplayName DefaultValue="Fun (online)"/&gt;
    &lt;Description DefaultValue="Fun (online)"/&gt;
    &lt;Capabilities&gt;
      &lt;Capability Name="Workbook" /&gt;
    &lt;/Capabilities&gt;
    &lt;DefaultSettings&gt;
      &lt;SourceLocation DefaultValue="https://localhost/PRODSERVER/Fun/addin_online/Home.html" /&gt;
    &lt;/DefaultSettings&gt;
    &lt;Permissions&gt;ReadWriteDocument&lt;/Permissions&gt;
  &lt;/OfficeApp&gt;
  </code></pre>
  
  <p>And <code>Home.html</code></p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
    &lt;head&gt;
      &lt;meta charset="UTF-8" /&gt;
      &lt;meta http-equiv="X-UA-Compatible" content="IE=Edge" /&gt;
      &lt;title&gt;Fun (online)&lt;/title&gt;
  
      &lt;script src="https://ajax.aspnetcdn.com/ajax/jQuery/jquery-2.1.4.min.js"&gt;&lt;/script&gt;
      &lt;script src="https://appsforoffice.microsoft.com/lib/1/hosted/office.js"&gt;&lt;/script&gt;
      &lt;script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"&gt;&lt;/script&gt;
  
      &lt;script src="js/Notification.js"&gt;&lt;/script&gt;
      &lt;script src="js/Home.js"&gt;&lt;/script&gt;
  
      &lt;link href="css/Common.css" rel="stylesheet" type="text/css" /&gt;
      &lt;link href="css/Office.css" rel="stylesheet" type="text/css" /&gt;
      &lt;link rel="stylesheet" href="https://appsforoffice.microsoft.com/fabric/1.0/fabric.min.css"&gt;
      &lt;link rel="stylesheet" href="https://appsforoffice.microsoft.com/fabric/1.0/fabric.components.min.css"&gt;
  
    &lt;/head&gt;
    &lt;body class="ms-font-m"&gt;
      &lt;div class="padding"&gt;
        &lt;button class="ms-Button" id="open"&gt;open&lt;/button&gt;
      &lt;/div&gt;
    &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>