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Cybersecurity Stocks Gain 12% in a Week

A flaw in the programming language behind about 69% of websites where the language is known was fixed this week, and security software stocks rose.

Author

Jacob Radke
October 25, 2026 • Read Time: 1 minute

Cybersecurity stocks around the PHP incident

The programming language behind about 69% of websites carried a flaw for more than a decade. In 2024 its developers spotted part of it, but according to the PHP Foundation every fix had trade-offs and there was no known way to exploit it, so work on a fix stalled.

In August, Wiz, a cybersecurity firm owned by Alphabet, used AI tools from OpenAI and Google to target the code. Wiz says it found the first flaw on August 19 and had working attacks by August 21, which meant a hacker could take over the computer running a site that uses this programming language.

Developers released the fix October 21, after hackers had started trying it, with several sites going offline altogether as a precaution.

Eleven security software companies worth more than $5 billion each rose 12% on average this week while the S&P 500 fell 0.5%.

Line chart of price change from the Oct. 16 close through Oct. 23 for 11 security software companies worth more than $5 billion and the S&P 500. The group's average rose 12.1% while the S&P 500 fell 0.5%. Zscaler gained 23.0% and Varonis 0.3%. The Oct. 21 PHP security patch release is marked. Dividends excluded.

We continue to monitor how AI is changing the way software flaws are found, and how companies and markets respond.

Until next week,

Jacob