Three sexual assault victims are accusing Uber of failing to warn them that predators posing as drivers were targeting young women leaving Los Angeles nightclubs, casting a growing cloud over the ride-sharing firm as it prepares to follow rival Lyft into publicly-traded stock markets.

The San Francisco-based company’s inaction left them “vulnerable sitting ducks,” the women said in a lawsuit filed in Los Angeles County Superior Court that argued the firm was made aware of the risk of fake drivers as early as 2016.