GHSA-pgcc-vfmc-7cw5

### 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