Mubasher: Facebook shares retreated sharply following the recent security crisis, while its CEO Mark Zuckerberg’s net fortune was hit by the news and updates.

Facebook's stock fell by around 7% to $172.56 per share at Monday’s closing, reducing the social network’s total market value by about $27 billion, while Zuckerberg, who is ranked the world’s fifth richest person according to Bloomberg's billionaire index, lost $5.1 billion of his wealth.

Reports previously showed that London-based data analysis company Cambridge Analytica had illegally acquired private information of more than 50 million Facebook users, raising concerns over the giant social network’s credibility and data protection system.

The UK firm was believed to have used this information to help US President Donald Trump during his presidential campaign.

These allegations are considered fraudulent and “we will take whatever steps are required to see that the data in question is deleted once and for all and take action against all offending parties,” Facebook deputy general counsel Paul Grewal told the Times.

This incident further sparked questions from US and UK politicians over Facebook’s privacy rules, as UK prime minister Theresa May’s spokesperson called the allegations "very concerning".

"The lid is being opened on the black box of Facebook's data practices, and the picture is not pretty," the BBC reported, citing University of Maryland law professor Frank Pasquale.