Key Highlights

● Fortinet fell during the regular session for unclear reasons.

● Shares then plunged further after its earnings report.

● One recap cited a gross-margin shortfall.

● The decline came despite a broader semiconductor-led Nasdaq gain.

Fortinet shares fell during Wednesday's regular session, October 28, then dropped far more steeply in extended trading after a quarterly report that one market recap said included a gross-margin shortfall.

Fortinet (NASDAQ:FTNT) endured a rough Wednesday on two fronts. The cybersecurity company's shares slid during the regular session, making it one of the decliners on an otherwise positive day for the Nasdaq-100. Then, after the closing bell, the stock plunged once its third-quarter results showed a gross margin that fell short of forecasts.

Two Legs Down

The regular-session decline came before the earnings release, and no specific catalyst for that earlier drop was cited. The stock moved lower on a day when investors were favoring semiconductor stocks over software within the technology sector.

The bigger move came later. Shares tumbled in extended trading after the results. Reports differed on the size of that after-hours plunge, but all described a steep drop that dwarfed the regular-session slide.

The Margin Question

Gross margin measures how much of each dollar of revenue a company keeps after paying the direct costs of producing its products and services. For Fortinet, which sells firewall appliances alongside higher-margin subscriptions and support, the figure is a key signal of product mix and pricing power.

According to one market recap, the gross margin missed. Not every account was negative, though: another recap described the results as solid and said Fortinet raised its guidance. It was not clear which part of the report drove the sharp after-hours reaction.

A Wider Software Sell-Off

Fortinet was part of a broader after-hours retreat in software and internet names. ServiceNow (NYSE:NOW) tumbled after its results and guidance underwhelmed, and Tyler Technologies (NYSE:TYL) slid after trimming its revenue forecast. Alphabet (NASDAQ:GOOGL), the Nasdaq-100's heavyweight, slid sharply after missing estimates, dragging Nasdaq-100 futures lower overnight.

Earlier in the day, network-security peer F5 (NASDAQ:FFIV) tumbled after its fiscal 2027 growth guidance and a downgrade from Piper Sandler to Neutral. Gen Digital (NASDAQ:GEN), which focuses on consumer security, bucked the trend, jumping after the bell after raising its full-year outlook.

What to Watch

Despite Fortinet's slide, the Nasdaq-100 closed at 29,813.16, up 161.72 points, powered by a semiconductor rally after strong results from SK hynix (NASDAQ:SKHY). The Philadelphia Semiconductor Index rose for a fourth straight day to 11,684.00.

The immediate focus is Thursday's open, when the after-hours plunge meets full regular-session trading. Investors will dig into management's comments on the margin shortfall, product mix and demand for firewall upgrades, as well as any analyst rating changes.