This is not a phishing attack. See thread here:
Intellij Android Studio opens localhost page to login on github
Intellij support says that this is an Android Studio bug and recommends using a token as a workaround.
Generating the token
Log in to you GitHub account and navigate to Settings > Developer Settings > Personal Access Tokens
Click "Generate new token"
Add a note so you know this token is for Android Studio and then check the following boxes: repo, read:org, and gist
Click "Generate token"
Now copy the generated token and return to Android Studio.
Log In With Token From Android Studio
In Android Studio, Navigate to File > Settings > Version Control > GitHub
Select the '+' and then choose "Log In with token".
Paste the copied token and click "Add Account"