Twitter stock plunges amid uncertainty as user growth continues to stall even as revenue grows

Tepid user growth and ongoing uncertainty about its leadership are dragging Twitter's stock to its lowest level in over a year even though the short-messaging service reported sharply quarterly higher revenue.

Co-founder Jack Dorsey, who replaced Dick Costolo as CEO earlier this month, says Twitter is "not satisfied" with its user growth. But that's unlikely to change any time soon.

Chief Financial Officer Anthony Noto, said Tuesday that Twitter doesn't expect to see "sustained, meaningful growth" of its number of users until it reaches the mass market. This, he says, will take a considerable amount of time.

On average, Twitter had 316 million monthly active users in the second quarter, up less than 3 percent from the first quarter.

The company's stock was down almost 14 percent in afternoon trading.