After several failed attempts, he found one internal web page that did not require a username or any other information to access, The Telegraph reported on Monday.
"It had many links to different sections of Google services and infrastructure, but before I visited any section, I read something in the footer: 'Google Confidential'," the student wrote in a blog post in July.
"At that point, I stopped poking at the website and reported the issue right away," he added. Google's security team replied saying they were looking into the issue.
"I thought to myself 'Cool, this is probably a small thing that isn't worth a dime, the website probably had some technical stuff about Google servers and nothing really important'," he recalled.
"I don't know what the website did contain, but some weeks later I got an email right after getting out of school that said my report was worth much more than a dime."
Google later paid him $10,000 and fixed the bug. Google runs a Vulnerability Reward Programme (VRP), offering monetary rewards to reporters who flag bugs. Earlier this year, Google increased the bounty for finding a bug in its proprietary Android OS to as much as $2,00,000.