There is a tendency to think of headline-grabbing security threats as a result of elite hacking groups with sophisticated operations. Sometimes, though, a massive digital gateway opens up because of a single, simple human oversight. Security researchers recently uncovered a vulnerability nicknamed FlagLeft, which quietly turned several popular Microsoft 365 apps into a silent pipeline for account takeovers. The vulnerability impacted several tools on Android devices, putting billions of unwitting users at risk. A shortcut left in production The underlying cause of this massive scare is surprisingly basic. While analyzing Microsoft’s mobile lineup, cybersecurity firm Enclave and researcher Ofek Levin…