It was under an investigation based off of a completely bullshit book (Clinton Cash, the author even admitted they don't have evidence to back up most of the assertions when pressed by media, IIRC) that went nowhere. As for the reports of it being a slush fund, that was largely a pushed by partisan conservative blogs looking to try to make the Clinton Foundation into a campaign issue despite it being almost entirely above board (minus a few minor issues that were more bureaucratic than anything else).