Grav vulnerable to Privilege Escalation and Authenticated Remote Code Execution via Twig Injection

Grav is a file-based Web platform. Prior to 1.8.0-beta.27, a user with admin panel access and permissions to create or edit pages in Grav CMS can enable Twig processing in the page frontmatter. By injecting malicious Twig expressions, the user can escalate their privileges to admin or execute arbitrary system commands via the scheduler API. This results in both Privilege Escalation (PE) and Remote Code Execution (RCE) vulnerabilities. This vulnerability is fixed in 1.8.0-beta.27.