InstantCMS is a free and open source content management system. In photo upload function in the photo album page there is no input validation taking place. Due to this attackers are able to inject the XSS (Cross Site Scripting) payload and execute. This vulnerability is fixed in 2.16.3.
https://github.com/instantsoft/icms2/security/advisories/GHSA-f6cf-jg84-fw29
https://github.com/instantsoft/icms2/commit/e02de2fa1850bb40c9b2050b9256c838a0ea7aa3