Grav is a file-based Web-platform built in PHP. Grav is subject to a server side template injection (SSTI) vulnerability. The fix for another SSTI vulnerability using "|map", "|filter" and "|reduce" twigs implemented in the commit "71bbed1" introduces bypass of the denylist due to incorrect return value from "isDangerousFunction()", which allows to execute the payload prepending double backslash ("\\"). The "isDangerousFunction()" check in version 1.7.42 and onwards retuns "false" value instead of "true" when the "\" symbol is found in the "$name". This vulnerability can be exploited if the attacker has access to: 1. an Administrator account, or 2. a non-administrator, user account that has Admin panel access and Create/Update page permissions. A fix for this vulnerability has been introduced in commit "b4c6210" and is included in release version "1.7.42.2". Users are advised to upgrade. There are no known workarounds for this vulnerability.