Google bug reveals Web stats
Search engine Google has acted quickly to plug an embarrassing hole in its Sitemaps facility. Visitors who 'verified' that they owned a site with Sitemaps could see private information about the site.
Sitemaps is a facility provided by Google that provides webmasters with information about their sites. Some of it - such as 'links' and 'inurl' - is meant to be public but other data is supposedly only available to the site owners. A bug crept in that allowed anyone to claim they had a right to see the information.
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Inside Google Sitemaps: Site Verification
When we first started showing statistics a couple of months ago, we put a system in place to prevent anyone other than site owners from seeing stats for a site. We ask each site owner to place a unique file on the site and then we check to see if that file exists. When we do that check, we first make sure that the server isn't misconfigured to return a valid page when a request is made for a page that doesn't exist. We only verify sites that are configured correctly. You can read more about that process in our documentation.