CVE-2026-55741: Cotonti CSRF in admin.config.php allows unauthorized configuration changes

Cotonti 1.0.0 (master branch, commit f43f1fc3) is vulnerable to Cross-Site Request Forgery in the administration configuration handler. In system/admin/admin.config.php, the configuration update action ('a=update') processes POST data via cotconfigupdateoptions() without calling cotcheckxg() to validate the anti-CSRF token (the 'x' parameter), unlike other admin handlers (e.g. admin.structure.php, admin.cache.php). A remote attacker who lures an authenticated administrator into visiting a malicious page can force the browser to submit a forged request that modifies arbitrary core, module, or plugin configuration options, which can be leveraged to weaken security or enable further compromise.