Flight is an extensible micro-framework for PHP. Prior to 3.18.1, the make:controller CLI command calls mkdir(..., recursive: true) on a path built from the user-supplied controller name, before Nette's class-name validation runs. The class-file write is correctly rejected by Nette when the name contains /, but the recursive directory creation side effect is already committed — including directories located outside the project root through ../ traversal. This vulnerability is fixed in 3.18.1.