Due to reports it has been validated that internal workspaces in Neos are accessible without authentication. Some users assumed this is a planned feature but it is not. A workspace preview should be an additional feature with respective security measures in place.
Note that this only allows reading of internal workspaces not writing. And for clarification, an internal workspace is a workspace that is non public and doesn't have an owner.
Given that an internal workspace exists in your installation, it is possible to view a page in context of that workspace by opening a link in this format:
https://domain/path/to/page.html@workspace-name
T
It has been discovered that TYPO3 Neos is vulnerable to Privilege Escalation. Logged in editors could access, create and modify content nodes that exist in the workspace of other editors.
Cross-Site Scripting (XSS) vulnerabilities in Neos
It has been discovered that Neos is vulnerable to several XSS attacks. Through these vulnerabilities, an attacker could tamper with page rendering, redirect victims to a fake login page, or capture user credentials (such as cookies). With the potential backdoor upload an attacker could gain access to the server itself, to an extent mainly limited by the server setup.