Grav 2.0.15 before 2.2.2 Arbitrary Static Method Call via Flex Form replace-name@

Grav from 2.0.15 before 2.2.2 contains an allowlist bypass vulnerability that allows page editors to call arbitrary public static methods by renaming Flex form fields with replace-name@. Attackers with page-edit permission can smuggle data-*@ directives past the callable check to invoke Folder::delete, Folder::move, or Utils::download, deleting directories, overwriting files, or reading files.