Anthropic’s latest AI announcement has sent shockwaves across global financial markets, sparking a sharp sell-off in US software and cybersecurity stocks. The reaction followed the company’s decision to limit the release of its powerful new AI model, Claude Mythos, after identifying its potential to uncover long-hidden cybersecurity vulnerabilities.
According to reports, Anthropic restricted access to this advanced model to a select group of around 40 major technology companies, including Microsoft and Google. As a result, investor sentiment quickly turned negative, particularly toward cybersecurity firms. Shares of major players such as Zscaler, Cloudflare, Okta, and CrowdStrike declined significantly, reflecting growing concerns about the disruptive impact of AI on the industry.
Moreover, the broader market also felt the pressure. The S&P 500 Software and Services Index dropped 2.6% on April 9, extending its overall decline to 25.5% since January. This makes it one of the worst-performing segments of the US market in 2026. At the same time, cybersecurity companies were among the hardest hit, with Cloudflare, Okta, CrowdStrike, and SentinelOne falling between 4.9% and 6.5%.
In addition, Zscaler emerged as one of the biggest losers on the S&P 500, plunging 8.8% after brokerage firm BTIG downgraded the stock from “buy” to “neutral,” citing concerns around weakening demand and intensifying competition. Consequently, the sell-off extended beyond cybersecurity into the broader enterprise software sector.
Companies such as Atlassian, Workday, Adobe, Salesforce, and Intuit also recorded declines ranging from 3.7% to 6.8%. Furthermore, the impact was not limited to the United States. European technology firms, including SAP, Capgemini, and Temenos, also experienced losses between 3% and 7%, indicating a global ripple effect.
However, the market reaction was not solely driven by the existence of a single AI model. Instead, it reflected deeper concerns about what such technology represents for the future of cybersecurity and enterprise software. If AI systems like Claude Mythos can detect vulnerabilities that have remained hidden for years, it raises critical questions about the effectiveness and value of existing cybersecurity solutions.
“We’re getting back to being concerned about the prior software-specific concerns stemming from AI and private credit that are coming back to the fore,” said Sosnick, chief market analyst at Interactive Brokers.
Earlier in the week, the software sector had briefly stabilized בעקבות optimism surrounding a potential US-Iran ceasefire, which had improved overall market sentiment. Nevertheless, Anthropic’s announcement quickly reversed those gains, highlighting the fragility of current market confidence.
This development also echoes earlier disruptions caused by Anthropic. In January, the company launched 11 open-source plugins for its Claude Cowork tool, triggering what analysts described as a “SaaSpocalypse.” That event wiped out approximately $285 billion in market value across software, legal tech, and financial services stocks in a single trading session.
Overall, the emergence of highly advanced AI models like Claude Mythos is reshaping market dynamics and forcing investors to reassess the long-term outlook of the software and cybersecurity industries.
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