Open Redirect Vulnerability

Thanks to PwnFunction

YT - Open Redirection vulnerability Explained

Open redirect is common feature used to implement redirect the user from one page to another such as redirecting user during LOGIN, REGISTRATION, PASSWORD RESET etc. One such example in php is below.

<?php 
    $redirect_to = $GET['redirect_to'];
    header("Location: $redirect_to");
    exit;

The above code perform the redirection to the url provided in the get request on the server side.

On the client side, the redirection can happen with JS or HTML
JS - windows.location variable
HTML - <meta> tags

Frameworks
Flask - redirect()

Usually open redirect is chained with other exploits such as SSRF or XSS