Up to 500million Andriod users who use or have used Android software could be at risk from having personal information shared after tests revealed it’s impossible to clear data from many devices.
A report by Cambridge University showed that private text messages, images, videos and email details can be recovered, even after a total wipe – or factory reset – has been done.
It means that people who have given away, sold or lost phones are now at risk from having their personal details and any private or sensitive information in messages or emails seen by whoever now has their old phone.

They could also access third party applications. Many phone users store financial information and do their banking through some of the most popular apps on tablets and phones such as Halifax and Nat West.

Researchers also recovered Google authentication tokens, allowing to access services which are synced across a number of devices, including Gmail, YouTube, and any images or videos stored using Google cloud services. .. see more

source: Dailymail UK