A Cambridge Analytica researcher who collected data on millions of Facebook users also sold user data to "a handful" of other firms, Facebook CEO Mark Zuckerberg testified before Congress on Wednesday. The researcher, Aleksandr Kogan gave data to the firm Eunoia Technologies, Zuckerberg previously testified. When pushed on Tuesday, Zuckerberg admitted that Kogan had given data to other firms, but did not disclose the exact number or their names. Zuckerberg said Facebook asked those companies to delete the data in 2015, but that they might have retained it. "They all represented to us that they had," he testified. "It wasn't until about a month ago that new reports surfaced and suggested that they hadn't, which is what has kicked off us needing to do this full audit and investigation and investigate all these other apps that have come up."