Description

Stored cross-site scripting (also known as second-order or persistent XSS) arises when an application receives data from an untrusted source and includes that data within its later HTTP responses in an unsafe way.

Proof of Concept

Steps to Reproduce:-
=> Install the WebApp and Setup it
=> Login in to webAPP using Admin Creds. 
=> Navigate to "http://localhost/MineWebCMS-1.15.2/admin/navbar"
=> Add/Edit a Link Select "Drop-Down Menu"
=> "Link Name" and "URL" Both Input are Vulnerable to Exploit Simple XSS 
=>  Payload : <script>alert(1);</script>
=> XSS will trigger on "http://localhost/MineWebCMS-1.15.2/" Aka WebApp HOME Page

Note : As you can see this simple payload working in those two inputs as normally . Whole WebApp Admin Input Structure is allow to do HTML Injection or XSS Injection 

Here i attach two ScreenShot for Easy UnderStand

Impact

If an attacker can control a script that is executed in the victim’s browser, then they can typically fully compromise that user.