PHP VanillaForum 

The vulnerability exists due to insufficient sanitization of user-supplied data passed to "index.php?p=/dashboard/settings/branding" URL. A remote attacker can permanently inject and execute arbitrary HTML and script code in user's browser in context of vulnerable website.
Successful exploitation of this vulnerability may allow a remote attacker to steal potentially sensitive information, change appearance of the web page, perform phishing and drive-by-download attacks.

Version: 2.6.3
OS: Windows 10, Linux
PHP: 7
URL: index.php?p=/dashboard/settings/branding