SSRF via Referer header in ChurchCRM allows server-side HTTP/HTTPS requests to arbitrary hosts

ChurchCRM is an open-source church management system. Prior to 6.5.3, it is possible to trigger server-side HTTP/HTTPS requests to arbitrary hosts (SSRF) by supplying a crafted URL in the Referer request header. The server subsequently makes an outbound request to the attacker-controlled domain, confirmed via OAST. This vulnerability is fixed in 6.5.3.