CVE-2026-33676: Vikunja has Cross-Project Information Disclosure via Task Relations — Missing Authorization Check on Related Task Read

When the Vikunja API returns tasks, it populates the related_tasks field with full task objects for all related tasks without checking whether the requesting user has read permission on those tasks’ projects. An authenticated user who can read a task that has cross-project relations will receive full details (title, description, due dates, priority, percent completion, project ID, etc.) of tasks in projects they have no access to.