The risk that a company may decline in share price because of negative news coverage. For example, rumors that a company's earnings are declining may cause shareholders to sell their stock. Even if the news itself is not true, headline risk can cause significant volatility for the stock in the short-term. For this reason, companies often price out the news by slowly leaking information before it is announced to minimize surprises and reduce the power of false rumors. See also: CNN effect.
The possibility a negative news story will spread to other media outlets and cause a significant change in the value of an investment. For example, an unconfirmed report of a corporate management shakeup might be picked up by competing newspapers and television networks, thus causing a sharp decline in the company's stock price. The firm's stock price is likely to be subject to substantial volatility even though the story eventually proves false.