CVE-2026-39963 Serendipity: Host Header Injection enables authentication cookie scoping to an attacker-controlled domain

Serendipity is a PHP-powered weblog engine. In versions 2.6-beta2 and below, the serendipitysetCookie function in include/functionsconfig.inc.php uses $SERVER'HTTPHOST' without validation as the domain parameter of setcookie. An attacker who can influence the Host header at login time, such as vi...