October is a Content Management System (CMS) and web platform to assist with development workflow. An authenticated backend user with the editor.cms_pages, editor.cms_layouts, or editor.cms_partials permissions who would normally not be permitted to provide PHP code to be executed by the CMS due to cms.safe_mode being enabled can write specific Twig code to escape the Twig sandbox and execute arbitrary PHP. This issue has been patched in 3.4.15.