What does "discover known accounts" permission mean? I am not sure what an app can do to me if it is able to discover my account, to what extent?

Thank you very much.
This permission is of moderate-high importance. This allows the
  application to read what accounts you have and the usernames
  associated with them. It allows the app to interact with permission
  related to that account. An example would be an app that was restoring
  your contact, would discover your Google account then send you to
  Google's login screen. It doesn't actually get to see your password,
  but it gets to work with the account. This is also legitimately used
  by applications to add contacts to your accounts, such as dialer
  replacements and contact managers/backup/sync/etc.


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