However, it sounds like Google was ready to shut down the platform regardless of this issue, citing in its announcement the consumer version's "very low usage".
As part of an audit of APIs, Google also discovered that Google+ had also been permitting developers to obtain data from users who never wanted it to be shared publicly - but a bug in the API meant they could collect data even if it was explicitly marked non-public through Google's privacy settings.
The company says it didn't find any evidence that any of the affected personal information was misused.
Google said it hasn't yet found any evidence that the data obtained as a result of the bug was misused. While Google+ will no longer be a consumer product, new features will be coming soon to turn it into an enterprise-focused platform.
A spokeswoman for Google said that whenever user data may have been affected it determines whether to tell people based on a number of criteria.
Despite the size of the security flaw, Google executives opted not to disclose the problem at the time because they feared trouble from regulators after the intense criticism encountered by Facebook over its privacy woes, according to the Wall Street Journal. That said, social media is the business where Google has failed to mark its presence.
A software glitch in the social site gave outside developers potential access to private Google+ profile data between 2015 and March 2018, when internal investigators discovered and fixed the issue, the report said.
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Google's post said the API failures came to light through a review dubbed Project Strobe.
Google will take the next 10 months to kill off G+ for consumers, finishing it off by August of 2019. Google and Apple are both now giving users more control over their data and the ability to limit what third parties can access.
The bug allowed app developers to access information like names, email addresses, occupation, gender and more.
Google came under criticism for refusing to send a top executive to a Senate Intelligence Committee hearing on 5 September about efforts to counteract foreign influence in U.S. elections and political discourse.
Google also announced new API changes in an effort to restrict developers' access to data on Android devices and Gmail.
Apps will be required to inform users what data they will have access to. The company was the target of a massive class action lawsuit in the United Kingdom after 4 million users had their personal data collected and allegedly used for targeted advertising.
Additionally, Google is limiting which apps can seek permission to users' consumer Gmail data.
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