When you use a Google or other connected account (like Facebook) to sign in to another website, a small trust gets established. This might be ok for a short time, but that trust stays until you delete. Over time, you’ll end up with alot of these trusts. The security implications of this are unknown but severe.
To remove the unwanted and/or unknown trusts, login to your Google account via Google.com.
Then click on your picture to the top right corner, and click on the link for “Account”.
Click on the Security tab up top, and then on “Apps and Websites – View All”.
From here, go down the list and click the “Revoke” button off to the right to remove access for the particular trust. If you’re not sure, remove it! You can always add it back.