Came across this trivial problem recently.
We keep using our Google based sign-in for plenty of websites.
However, every time we authorize a website to use Google Login, the website also gets access to certain other things like managing our contacts, or managing photos, etc.
To see the list of websites which currently have the permissions to modify something, we can log onto -
https://security.google.com/settings/security/permissions?pli=1
From here, we can see the list of all the apps / websites who have access to our Google account.
For a more detailed explanation, refer the Google Support page -
https://support.google.com/accounts/answer/3466521?hl=en