N26 is a smartphone only bank that was originally launched in Germany and has big backers like Peter Thiel behind it; Vincent Haupert, a PhD student at the University of Erlangen-Nuernberg, told the Chaos Communications Congress in Hamburg how he and two colleagues found N26 security defenses riddled with holes that could have been used to defraud thousands of users; Haupert presented his findings to the bank and they have since stated that the issues found have been addressed. Source
