Google has pushed out an emergency security update that affects millions of people who rely on its software every day, from Android phones to Chrome browsers and Gmail inboxes. The move underlines how quickly a single flaw can ripple across the company’s vast ecosystem and why users cannot afford to ignore those seemingly routine prompts

The world’s largest technology companies are racing to manage disruption affecting thousands of employees on US work visas, after new social media screening rules led to delays at American embassies a...