Facebook chief executive Mark Zuckerberg said the tech giant has been investing heavily in “safety, security and privacy” after being rocked by concerns of manipulation. Facebook shares went into a freefall 25 July as a stunningly weak financial outlook raised fresh concerns for the social networking giant as it tries to recover from the impact of data protection scandals and investigations. After-hours trade saw Facebook shares plunge by some 21%, wiping out an estimated $130 billion in market value if the slump is confirmed at 26 July market opening.