Facebook Inc. confronted an intensifying crisis as political leaders in the U.S. and Europe called for aggressive inquiries into whether the technology giant failed to stop improper access and handling of user data, scrutiny that sent the company’s stock to its biggest decline in four years.
The uproar pushed Facebook’s stock down 6.8% to $172.56 Monday, wiping out about $36 billion in market value as the episode reignited concerns over how Facebook, Alphabet Inc.’s Google and other internet firms handle user data that is...