Zenefits co-founder and CEO Parker Conrad has stepped down and been replaced by COO David Sacks. The company has also added three board members, including PayPal co-founder Peter Thiel. The news follows a Buzzfeed report that Zenefits had been allowing unlicensed brokers to illegally sell health insurance. The company has raised about $600 million in funding, most recently securing $513 million last year at a valuation of $4.5 billion. Its investors include Andreessen Horowitz, Founders Fund and General Catalyst Partners, among others.