This vulnerability (CVE-2026-65513) is an unauthenticated cross-site scripting (XSS) issue in NSquared Simply Schedule Appointments versions up to 1.6.12.10. It stems from improper neutralization of input during web page generation (CWE-79), allowing attackers to inject malicious scripts that execute in the context of the victim's browser. The CVSS 3.1 base score is 7.1, reflecting network attack vector, low attack complexity, no privileges required, user interaction required, and impacts to confidentiality, integrity, and availability. The vulnerability is published and assigned but lacks an official remediation or patch at this time.

Successful exploitation could allow an attacker to execute arbitrary scripts in the context of the affected web application, potentially leading to partial disclosure of sensitive information, modification of data, or disruption of service. Because the vulnerability is unauthenticated, it can be exploited by remote attackers without credentials. The impact affects confidentiality, integrity, and availability to a limited extent as indicated by the CVSS vector.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, users should consider applying any available workarounds or input validation controls if possible. Monitor vendor communications for updates on patches or official mitigations.