Grav: Remote code execution via unrestricted callable in Blueprint::dynamicData()

Grav is a file-based Web platform. Prior to 2.0.7, Grav Blueprint::dynamicData() in system/src/Grav/Common/Data/Blueprint.php sends an editor-controlled Class::method provider and arguments to call_user_func_array() without rejecting dangerous callback parameters. An account with admin.pages or api.pages.write can use Grav\Common\Utils::arrayFilterRecursive() as a trampoline with system as the callback, place a command in page frontmatter, and execute that command as the web server user when the page is viewed. This issue is fixed in version 2.0.7.