Description

The htmlspecialchars function does not escape special characters like single quote, and the $prefix parameter can lead to reflected XSS

Proof of Concept

https://demo.livehelperchat.com/site_admin/user/avatarbuilder/1?_=1640314779051&prefix=123%27);})});%20alert(%27xss%27);//

Impact

XSS can have huge implications for a web application and its users. User accounts can be hijacked, change the html screen and insult the organization. Credentials could be stolen, sensitive data could be exfiltrated, and lastly, access to your client computers can be obtained.