This vulnerability (CVE-2026-66596) is an unauthenticated Cross-Site Scripting (XSS) issue in the Newsletter product by Stefano Lissa, affecting versions up to 9.3.3. The flaw stems from improper neutralization of input during web page generation, classified under CWE-79. The CVSS 3.1 base score is 7.1, indicating high severity, with an attack vector of network, low attack complexity, no privileges required, user interaction required, and scope changed. The impact includes low confidentiality, integrity, and availability impacts. There is no vendor advisory or patch information available at this time.

Successful exploitation of this vulnerability could allow an attacker to execute arbitrary scripts in the context of the affected web application without authentication. This can lead to partial compromise of confidentiality, integrity, and availability of the affected system or user data. However, no known exploits are reported in the wild.

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 mitigations recommended by the vendor once available. Monitoring vendor channels for updates is advised.