Grav Server-side Template Injection (SSTI) via Twig Default Filters

Grav is a flat-file content management system. Prior to version 1.7.42, the patch for CVE-2022-2073, a server-side template injection vulnerability in Grav leveraging the default filter() function, did not block other built-in functions exposed by Twig's Core Extension that could be used to invoke arbitrary unsafe functions, thereby allowing for remote code execution. A patch in version 1.74.2 overrides the built-in Twig map() and reduce() filter functions in system/src/Grav/Common/Twig/Extension/GravExtension.php to validate the argument passed to the filter in $arrow.