Why It Moved · Market · 2026-10-29

Why it moved, October 29: ServiceNow -27%, Fortinet -20%, Gen Digital +16%

On Thursday, October 29 the S&P 500 fell 0.4% and 405 of 503 member stocks finished higher. AI-infrastructure stocks fell a median 2.0%. These were the five biggest moves among S&P 500 stocks, and what was behind each.

Investigations

FTNT

The question

Revenue grew 26% from a year earlier and the company made money, yet the stock fell 25% around its results. What do the filings show that the headline didn't?

What the filings show

Insiders sold, none bought. Executives and directors sold about $36.2 million of stock in the 90 days to Oct 29, the largest seller $26.3 million. Sales are often planned or for taxes; purchases are rarer.
The timing. Results came out after the close on Oct 28. The stock moved -5.9% that day, before they were public (S&P 500 ETF +0.3%), and -20.1% the next day (S&P 500 ETF -0.4%).

What to watch

The next quarterly report (the quarter ending in September, filing due around November 2026): whether the outlook holds.

Sources: earnings release (8-K, 2026-10-28) · 10-Q (2026-07-30)

The biggest S&P 500 moves, October 29

Company	Move	vs usual day	Year to date	Where it stands
ServiceNow (NOW)	-27.0%	10.2x	-28.4%	-41% from high · below 200-day
Fortinet (FTNT)	-20.1%	10.2x	+75.2%	-29% from high · above 200-day
Gen Digital (GEN)	+15.8%	8.9x	+5.3%	-10% from high · above 200-day
Carvana (CVNA)	+15.5%	5.2x	-19.2%	-29% from high · below 200-day
Huntington Ingalls Industries (HII)	+13.4%	8.0x	-5.7%	-30% from high · below 200-day

"vs usual day" compares the move with the stock's average daily move (up or down) over the past year. "Where it stands" is the distance from the 52-week high and the position against the 200-day average. Stocks with a one-day change over 60% today (usually a spin-off or split) are left out; where a stock had such a jump earlier in the year, its longer-run columns show –.

What this means

ServiceNow (NOW) fell 27.0% as CNBC reported “ServiceNow shares plunge 27% to worst day ever after earnings revive AI disruption fears”¹. That is about 10 times its usual daily move. It was not alone: the other 6 software stocks in the S&P 500 fell a median 2.8%, 5 of the 6 lower (biggest: Fortinet -20.1%, Gen Digital +15.8%, Twilio -4.6%), after Reuters reported “Software stocks slide as Fortinet, ServiceNow fail to meet lofty investor expectations”². It reported quarterly results; options had priced a move of about ±21%.
Fortinet (FTNT) fell 20.1% as Reuters reported “Software stocks slide as Fortinet, ServiceNow fail to meet lofty investor expectations”². That is about 10 times its usual daily move. It moved with the rest of the software group (see ServiceNow above). It reported quarterly results; options had priced a move of about ±5%.
Gen Digital (GEN) rose 15.8% as Barron's reported “Gen Digital Surges. It Kills M&A Speculation While the Cyber Boom Drives an Earnings Beat”³. That is about 9 times its usual daily move. It reported quarterly results.
Carvana (CVNA) rose 15.5% as Investor's Business Daily reported “Carvana Soars: This Is How Much It's Defying Weak Used-Car Market”⁴. That is about 5 times its usual daily move. It reported quarterly results; options had priced a move of about ±3%.
Huntington Ingalls Industries (HII) rose 13.4%. That is about 8 times its usual daily move. It was not alone: the other 12 aerospace and defense stocks in the S&P 500 rose a median 3.5%, 11 of the 12 higher (biggest: Textron +11.7%, Honeywell Aerospace -9.6%, L3Harris +6.9%), after Investing.com reported “Earnings call transcript: Textron beats Q3 2026 estimates, lifts outlook”⁵. It reported quarterly results.
A big one-day move tells you what the market learned that day, not where the stock goes next: large moves partly reverse about as often as they continue.

Sources

CNBC, Oct 29, 2026: ServiceNow shares plunge 27% to worst day ever after earnings revive AI disruption fears
Reuters, Oct 29, 2026: Software stocks slide as Fortinet, ServiceNow fail to meet lofty investor expectations
Barron's, Oct 29, 2026: Gen Digital Surges. It Kills M&A Speculation While the Cyber Boom Drives an Earnings Beat
Investor's Business Daily, Oct 29, 2026: Carvana Soars: This Is How Much It's Defying Weak Used-Car Market
Investing.com, Oct 29, 2026: Earnings call transcript: Textron beats Q3 2026 estimates, lifts outlook

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See plans

Prices from Torvanta's end-of-day data; filings from SEC EDGAR. News context is drawn from the coverage cited below and may not be the whole cause of a move. Research only, not investment advice or a recommendation to buy or sell any security. Rankings change as data changes and can be wrong. Torvanta and its founder may hold positions in securities discussed, and trade only after the information is published to all subscribers. Past performance does not guarantee future results.

More research

Insider & Short-Selling Daily, October 29 2026-10-29
Market brief, October 29: S&P 500 falls 0.4% as internet stocks slide 2026-10-29
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The Giants Monitor: the top 10 are 42.0% of the S&P 500 (week of October 26) 2026-10-29
Insider & Short-Selling Daily, October 28 2026-10-28
Market brief, October 28: S&P 500 rises 0.1% as software stocks slide 2026-10-28
Why it moved, October 28: Fortinet -27%, F5 -20%, ServiceNow -19% 2026-10-28
Midweek Movers: where the model's view shifted this week 2026-10-28
Insider & Short-Selling Daily, October 27 2026-10-27
Market brief, October 27: S&P 500 rises 0.6% as chip stocks rally 2026-10-27
Why it moved, October 27: Xylem -14%, Pentair +13%, Boeing -11% 2026-10-27
Dividend Watch, October 27: Vici Properties leads covered yields 2026-10-27

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