I pointed my browser at the website of a web developer I barely know, and the page returned was his home page, with the message "Welcome myname@gmail.com!"

Whoa. Where did it get my Gmail address? Never seen that before. I was logged in to that Google account at that time, but somehow that login account is accessible to someone whose web page I go to. That info sure isn't contained in any Apache logs, though certainly my IP address is. I am aware that Google makes all kinds of information available to users, unless one tells them not to.

  1. How does one prevent one's Gmail address from being transmitted to a website, so as to preserve some semblance of anonymity?
  2. How do you set up a website to get that info?

migrated from webmasters.stackexchange.com Aug 24 '15 at 19:04

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  • 1
    We might need to inspect the page's code to narrow down the possibilities, else we're guessing. – schroeder Aug 24 '15 at 19:07
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    If you provide the URL, we can take a look. – ThoriumBR Aug 24 '15 at 19:09
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    I am using Mac Firefox 40.0. Um, wait. What that web page showing me is a Google Drive pane, which says "You are signed in as xxxx@gmail.com". So does this mean that Google Drive is telling me who I am signed in as, but not telling the website owner who I am signed in as? I have no problem with that. – user618 Aug 24 '15 at 21:24
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    @Gewure that only works for detecting if someone is logged in to, for example, Google, not for obtaining the e-mail address. – user2428118 Sep 7 '15 at 16:24
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    @Gewure - I tried the "Demo" page: tomanthony.co.uk/tools/detect-social-network-logins (Thanks for the links). It appears to be working for Facebook, Google, and Google+, but not for Twitter. Perhaps this is temporary, or perhaps Twitter has changed their site and the script no longer works. – Kevin Fegan Nov 21 '15 at 1:12

The website is simply asking the Google login handler to display the information to you -- and then placing it on the website in such a fashion that it appears to be the website knowing your logged in account. But in truth it's just a tag to them, like <%InsertLoggedInName%> or something like that.

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