CVE-2026-28697: Craft CMS Vulnerable to Authenticated RCE via "craft.app.fs.write()" in Twig Templates

An authenticated administrator can achieve Remote Code Execution (RCE) by injecting a Server-Side Template Injection (SSTI) payload into Twig template fields (e.g., Email Templates). By calling the craft.app.fs.write() method, an attacker can write a malicious PHP script to a web-accessible directory and subsequently access it via the browser to execute arbitrary system commands.