However, one form of phishing, known as “man in the middle” (MITM), is hard to detect when an embedded browser framework (e.g., Chromium Embedded Framework - CEF) or another automation platform is being used for authentication. MITM intercepts the communications between a user and Google in real-time to gather the user’s credentials (including the second factor in some cases) and sign in. Because we can’t differentiate between a legitimate sign in and a MITM attack on these platforms, we will be blocking sign-ins from embedded browser frameworks starting in June. This is similar to the restriction on webview sign-ins announced in April 2016.
What developers need to know
The solution for developers currently using CEF for authentication is the same: browser-based OAuth authentication. Aside from being secure, it also enables users to see the full URL of the page where they are entering their credentials, reinforcing good anti-phishing practices. If you are a developer with an app that requires access to Google Account data, switch to using browser-based OAuth authentication today.