Vikunja is an open-source self-hosted task management platform. Prior to version 2.2.0, an authenticated user can read any task comment by ID, regardless of whether they have access to the task the comment belongs to, by substituting the task ID in the API URL with a task they do have access to. Version 2.2.0 fixes the issue.

Affected: Go: code.vikunja.io/api

An authenticated user can read any task comment by ID, regardless of whether they have access to the task the comment belongs to, by substituting the task ID in the API URL with a task they do have access to.

## Details

The `GET /api/v1/tasks/{taskID}/comments/{commentID}` endpoint performs an authorization check against the task ID provided in the URL path, then loads the comment by its own ID without verifying it belongs to that task.

### Root Cause

In `pkg/models/task_comment_permissions.go`, `CanRead` constructs a `Task` using the `TaskID` from the URL and checks `Task.CanRead`:

```go func (tc *TaskComment) CanRead(s *xorm.Session, a web.Auth) (bool, int, error) { t := Task{ID: tc.TaskID} return t.CanRead(s, a) } ```

In `pkg/models/task_comments.go`, `getTaskCommentSimple` loads the comment by ID only, with `NoAutoCondition()` explicitly disabling XORM's implicit struct-field filtering:

```go func getTaskCommentSimple(s *xorm.Session, tc *TaskComment) error { exists, err := s. Where("id = ?", tc.ID). NoAutoCondition(). Get(tc) // ... } ```

The generic web handler (`pkg/web/handler/read_one.go`) calls `CanRead` before `ReadOne`, so the permission check passes against the attacker-controlled task ID, and then `ReadOne` returns the comment from a completely different task.

### Attack Scenario

1. Attacker is authenticated and has read access to any task (task ID `A`) — e.g. their own task. 2. Attacker guesses or enumerates a…