Update November 18: Documented longer list of dangerous file extensions
Drupal core does not properly sanitize certain filenames on uploaded files, which can lead to files being interpreted as the incorrect extension and served as the wrong MIME type or executed as PHP for certain hosting configurations.
The File Example submodule within the Examples project does not properly sanitize certain filenames as described in SA-CORE-2020-012, along with other related vulnerabilities.
Therefore, File Example so is being removed from Examples until a version demonstrating file security best practices can added back in the future.
A vulnerability exists in the File module which allows an attacker to gain access to the file metadata of a permanent private file that they do not have access to by guessing the ID of the file.
The experimental Workspaces module allows you to create multiple workspaces on your site in which draft content can be edited before being published to the live workspace.
The Workspaces module doesn't sufficiently check access permissions when switching workspaces, leading to an access bypass vulnerability. An attacker might be able to see content before the site owner intends people to see the content.
This vulnerability is mitigated by the fact that sites are only vulnerable if they have installed the experimental Workspaces module.