Pierluigi Paganini April 20, 2019

Google this week announced that it is going to block login attempts from embedded browser frameworks to prevent man-in-the-middle (MiTM) phishing attacks.

Phishing attacks carried out by injecting malicious content in legitimate traffic are difficult to detect when attackers use an embedded browser framework or any other automated tool for authentication.

For example, the embedded browser framework Google offers Chromium Embedded Framework (CEF) that allows embedding Chromium-based browsers in other applications.

Google announced that starting from June, it will block sign-ins from these frameworks.

“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.” reads a blog post published by Google. “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.”

Google suggests developers currently using CEF for authentication to switch to the browser-based OAuth authentication.

The browser-based OAuth authentication also allows users to see the full URL of the page where they are entering their credentials, this could help them to avoid phishing websites mimicking legit ones.

“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,” continues Google.

“If you are a developer with an app that requires access to Google Account data, switch to using browser-based OAuth authentication today.”

Pierluigi Paganini

(SecurityAffairs – hacking, MiTM phishing attack)

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