The bug was caused by a software update in November, Google said in a blog post, adding that it was not due to a breach of its systems by a third party.
In October, Google's parent company Alphabet said it would be shutting down the social network after confirming that data from up to half a million user accounts may have leaked due to a bug in the system.
The leak was kept quiet for many months as the company feared regulatory intervention. Google chief executive Sundar Pichai was told of the decision to withhold the news of the leak after an internal committee had made the decision.
"In addition, we have also decided to accelerate the sunsetting of consumer Google+ from August 2019 to April 2019. While we recognise there are implications for developers, we want to ensure the protection of our users," Thacker said in the post.
He provided the following information about the company's investigation into the new bug:
"We have confirmed that the bug impacted approximately 52.5 million users in connection with a Google+ API.
"With respect to this API, apps that requested permission to view profile information that a user had added to their Google+ profile — like their name, email address, occupation, age — were granted permission to view profile information about that user even when set to not-public.
"In addition, apps with access to a user's Google+ profile data also had access to the profile data that had been shared with the consenting user by another Google+ user but that was not shared publicly.
"The bug did not give developers access to information such as financial data, national identification numbers, passwords, or similar data typically used for fraud or identity theft.
"No third party compromised our systems, and we have no evidence that the developers who inadvertently had this access for six days were aware of it or misused it in any way."