Security researchers Leigh-Anne Galloway & Timur Yunusov take the project that involved to analyze across the US and Europ using seven card readers in that belongs to different vendors such as iZettle, PayPal, Square, Square. They uncovered that more than half of the Mobile Point of Sales terminals are vulnerable to some form of attack. The team also found that its possible to carry out a man-in-the-middle attack using Bluetooth access to intercept the HTTPS traffic between the mobile application and the payment server.”]
Source: https://gbhackers.com/beware-square-paypal-mobile-pos/