Security Checkup shows all third-party apps that have access to you data

“Transparency and control have always been core data privacy principles, and we’re constantly working to ensure these principles are reflected in our products.Before a non-Google app is able to access your data, we show a permissions screen that clearly shows the types of data the app can access and how it can use that data.We strongly encourage you to review the permissions screen before granting access to any non-Google application”.

Source : Ensuring your security and privacy within Gmail