title: Component K2 is damaged, says class K2HelperHTML not found
body: <p>My Joomla powered website was hacked several days ago, after it was cleaned and restored, a problem emerged.</p>
  
  <p>On back-end, when I click <code>Components</code> -> <code>k2</code> and an fatal error appears:</p>
  
  <pre><code>Fatal error: Class 'K2HelperHTML' not found in ~/administrator/components/com_k2/k2.php on line 77
  </code></pre>
  
  <p>I compare this k2.php file with a working site's k2.php but no differenced was found.</p>
  
  <p>Then I inpsected the file where class K2HelperHTML was defined, which I believe is <code>~\administrator\components\com_k2\helpers\html.php</code>, it doesn't show any differenct from a working site's corresponding file. </p>
  
  <p>Now I'm stuck here, what should I do next to repair this.</p>