I’ll introduce the solution for when Google displays “Malicious apps may be installed on your device and used to access your account” (悪意のあるアプリがデバイスにインストールされ、アカウントへのアクセスに使用されている可能性がある).

Background: Woke Up to Find Mac Couldn't Log into Chrome

I woke up to find my Mac showing “Malicious apps may be installed on your device and used to access your account” (悪意のあるアプリがデバイスにインストールされ、アカウントへのアクセスに使用されている可能性がある) and couldn’t log into Chrome, which made me panic.

Here’s the situation organized chronologically:

• Last night around 23:30, everything was working normally
• Woke up to find Mac couldn't log into Chrome
• Android could still access Gmail while logged in

Resolution Log for Google's "Malicious apps may be installed on your device and used to access your account"

Remove Harmful Software When Logged Out

First, I proceeded with work referencing the following page that was displayed along with the “Malicious apps may be installed on your device and used to access your account” (悪意のあるアプリがデバイスにインストールされ、アカウントへのアクセスに使用されている可能性がある) message on the Google login screen.

📚 Remove harmful software when you’re logged out - Computer - Google Account Help (ログアウトされた場合に有害なソフトウェアを削除する - パソコン - Google アカウント ヘルプ)

Step 1: Remove unwanted or unsafe software

Since there didn’t seem to be any applicable apps, I quickly checked and didn’t remove anything.

Step 2: Remove untrusted browser extensions

To cut to the conclusion, this was the cause.

Remove Unwanted Ads, Pop-ups, and Malicious Software

📚 Remove unwanted ads, pop-ups, and malicious software - Computer - Google Chrome Help (望ましくない広告、ポップアップ、不正なソフトウェアを削除する - パソコン - Google Chrome ヘルプ)

Executing the Reset browser settings item allowed me to log into my Google account! 🎉

That’s all from the Gemba on resolving Google’s “Malicious apps may be installed on your device and used to access your account” issue.