Shares of Fortinet (FTNT 6.34%), a cybersecurity company, tumbled today after the company reported its third-quarter results. Fortinet beat Wall Street's consensus revenue and earnings estimates for the quarter, but investors latched onto the company's fourth-quarter sales guidance, which was lower than expected.
As a result, Fortinet stock was down by 6.3% as of 1:56 p.m. ET.
Image source: Getty Images.
Fortinet's third-quarter results were solid
Fortinet reported strong sales growth of 14% in the third quarter, reaching $1.72 billion and outpacing analysts' consensus estimate of $1.7 billion. The company's earnings were even more impressive, with non-GAAP (adjusted) earnings per share rising 17% to $0.74 -- surpassing Wall Street's estimate of $0.63 per share.
Adding to the positive news for the quarter was the fact that Fortinet's billings grew by 14% from the year-ago period to $1.81 billion, and the company achieved a record non-GAAP operating margin of 37%.
But despite this good news and the company beating analysts' consensus estimates, investors weren't happy with management's fourth-quarter sales guidance of $1.85 billion at the midpoint -- which was below analysts' consensus estimate of about $1.87 billion. The result of this led to a significant sell-off of Fortinet's stock today.

NASDAQ: FTNT
Key Data Points
A bit of an overreaction
With Fortinet growing sales and earnings at a steady pace and beating analysts' consensus estimates for both, today probably should have been a good day for Fortinet shareholders. Instead, investors overreacted to the fact that the company's fourth-quarter guidance was below expectations.
With today's sell-off, Fortinet's share price is up just 3.2% over the past year, compared to the S&P 500's 16.4% gains. Considering that solid quarterly results weren't enough to boost Fortinet's stock, investors should probably expect more volatility ahead.