Facebook CEO Mark Zuckerberg is to testify before Congress over his social network's role in the harvesting millions of users' data without their knowledge. Zuckerberg turned down a similar request from British MPs to answer questions on the role of the data firm Cambridge Analytica in the US presidential election campaign.
But the whistle-blower behind the scandal did agree to give evidence and, in doing so, revealed that the Brexit vote was also subject to manipulation by the firm.
Al Jazeera's Laurence Lee reports from Westminster.
