Shares of Fortinet (NASDAQ: FTNT) plunged 19.45% in after-hours trading on Thursday, following the cybersecurity firm's release of its second-quarter earnings report. Despite beating expectations for Q2, Fortinet's weaker-than-anticipated guidance for the third quarter sparked a sharp sell-off.

For the second quarter, Fortinet reported adjusted earnings per share of $0.64, surpassing the analyst consensus estimate of $0.59. Revenue came in at $1.63 billion, slightly above the expected $1.624 billion. The company's billings, a key metric for future revenue, grew 15% year-over-year to $1.78 billion.

However, investors focused on Fortinet's third-quarter outlook, which fell short of expectations. The company forecasts third-quarter revenue between $1.67 billion and $1.73 billion, with the midpoint below the analyst consensus of $1.71 billion. This guidance suggests potential challenges in maintaining its recent growth trajectory amid an increasingly competitive cybersecurity landscape and macroeconomic uncertainties.

Ken Xie, Founder, Chairman and Chief Executive Officer of Fortinet, commented on the results: "Our strong second quarter performance and consistent track record of growth are a direct result of our continued innovation and customer-first strategy, enabling us to beat our billings guidance for the quarter and raise our full year billings outlook."

Despite the disappointing Q3 guidance, Fortinet raised its full-year 2025 billings guidance midpoint by $100 million, indicating confidence in its long-term prospects. The company also announced an expansion of its FortiCloud services, introducing new offerings in identity management, secure file storage, and communication.

The significant after-hours stock plunge highlights the high expectations investors have for high-growth cybersecurity firms like Fortinet. While the company continues to show strong growth and innovation, the market's reaction underscores the importance of forward-looking guidance in today's volatile trading environment, especially amid ongoing global trade tensions and economic uncertainties.