vantage6 is an open-source infrastructure for privacy preserving analysis. Collaboration administrators can add extra organizations to their collaboration that can extend their influence. For example, organizations that they include can then create new users for which they know the passwords, and use that to read task results of other collaborations that that organization is involved in. This is only relatively trusted users - with access to manage a collaboration - are able to do this, which reduces the impact. This vulnerability was patched in version 4.5.0rc3.
The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.