August 15, 2022

TheCyberThrone

Thinking Security ! Always

Phishing Technique that bypasses MFA

A researcher (mrd0x) has developed a new phishing technique that can bypass MFA and steal login cookies through Microsoft Corp.’s Edge WebView2.

WebView2 is a runtime program, that provides web-based features in Microsoft 365 desktop applications using Microsoft Edge as a rendering engine. A PoC on phishing attack, dubbed “WebView2-Cookie-Stealer,” involves injecting malicious JavaScript code into websites loaded in an application that uses WebView 2.

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In an example, mrd0x injected a JavaScript keylogger into a legitimate Microsoft login form that was loaded using WebView2. The page itself renders normally, but with the JavaScript running in the background, the code captures anything the user types in and sends it back to the designated web server.

The method does not stop at keylogging. Taking advantage of the way WebView2 accepts JavaScript, mrd0x was also able to steal any cookies sent by the remote server after a user log in, including authentication codes.

Mrd0x also explains that WebView2 can be used to steal all available cookies for the current user in Google LLC’s Chrome. WebView2 allows an attacker to launch with an existing user data folder rather than creating a new one. The UDF contains all passwords, sessions, and bookmarks relating to the user.

This could be easily used to steal and import cookies using a simple Chrome extension such as EditThisCookie, the alarming thing is that the attack methodology completely bypasses MFA, one-time passwords, and security keys, since the cookies are stolen after the user is already logged in.

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To protect against attacks such as this, having a policy against downloading or running unapproved software or browser add-ins, and educating users on the dangers of running this type of software, can have a significant reduction in risk for the organization.

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