The File Force Download module for Drupal 7 implements hook_file_download() to add a Content-Disposition header when a file URL carries the download query parameter. In Drupal 7, returning a non-empty header array from that hook is itself a grant of access to the file. In versions 7.1.0 through 7.1.2, the module only delegated to other modules' hook_file_download() implementations when the file was in the private scheme. For every other scheme it returned its headers without any check. An unauthenticated visitor who appended download=1 to the URL of a file in the temporary:// scheme, or in a stream wrapper supplied by another module, could retrieve the file, overriding the access checks that