WordPress PVN Auth Popup 1.0.0 Cross Site Scripting Vulnerability

# Exploit Title: PVN Auth Popup <= 1.0.0 - Admin+ Stored XSS
# Exploit Author: Vuln Seeker Cybersecurity Team
# Vendor Homepage: https://wordpress.org/plugins/pvn-auth-popup/
# Version: <= 1.0.0
# Tested on: Firefox
# Contact me: [email protected]

Description

The plugin does not sanitise and escape some of its settings, which could
allow high privilege users such as admin to perform Stored Cross-Site
Scripting attacks even when the unfiltered_html capability is disallowed
(for example in multisite setup)
Proof of Concept

1. Go to https://example.com/wp-admin/admin.php?page=pvn_auth_popup
2. In the first section, enter the payload `"><script>alert(1)</script>`
for the "Login text" input
3. Save and see the XSS

Note: Other fields are likely vulnerable