Summary Kimai 2.56.0 contains authenticated cross-site request forgery issues in its default team creation shortcuts for projects, customers, and activities. These endpoints are exposed through "GET" routes and directly create or reuse a "Team", add the current user as teamlead, and bind the target object to that team. As a result, an attacker can trick a logged-in user with the required permissions into visiting a malicious page and cause unauthorized changes to team, teamlead, and object-binding relationships. This is a real authorization-structure modification issue rather than a harmless UI shortcut. Details The issue affects at least the following routes: - "GET /en/admin/project/{id}/create_team" - "GET /en/admin/customer/{id}/create_team" - "GET /en/admin/activity/{id}/create_team" Each of these routes is a "GET" endpoint, yet each performs persistent writes that alter authorization structure: - create or reuse a "Team" - add the current user as "teamlead" - bind the target "Project", "Customer", or "Activity" to that team A PoC was provided, but removed for security reasons. Impact This vulnerability allows an attacker to remotely alter permission topology while the victim is logged in. A successful exploit can create or reuse a team, assign the victim as its teamlead, and bind a project, customer, or activity to that team without intentional user action. The pre-requisite is, that the logged-in user already has access to manage permissions of the object in question. Because these routes modify authorization structure rather than a simple personal preference, the business impact can extend into visibility rules, assignment scope, team-based access control, reporting, and later privilege-expansion chains. This makes the issue materially more serious than a low-value cosmetic CSRF. Solution - The routes have been moved to API "POST" endpoints See https://www.kimai.org/en/security/ghsa-pgcc-vfmc-7cw5