Cybersecurity stocks decline following leak of Anthropic’s Mythos

Mar 27, 2026

Cybersecurity stocks declined following the leak of Anthropic's unreleased Claude Mythos AI model, which Anthropic attributed to human error in a content management system misconfiguration unrelated to its AI tools. The incident intensified investor fears that next-generation AI models could autonomously identify vulnerabilities and bypass traditional defenses, potentially reducing reliance on legacy security products from established vendors. Fortinet shares fell 3.62% to $78.10 despite no company-specific news, reflecting sector-wide concerns about AI disruption. Anthropic had previously introduced an AI tool designed to autonomously hunt software vulnerabilities, sparking worries that AI-enabled offerings from emerging players could challenge established security suites deeply embedded in enterprise networks.

Anthropic data leak and Claude Mythos exposure

▪Anthropic said the data exposure issue was unrelated to its AI tools
▪Anthropic said the data exposure issue was caused by human error
▪The Anthropic data leak reportedly revealed details about an unreleased model called Claude Mythos

AI disruption concerns for traditional cybersecurity vendors

▪Anthropic previously introduced an AI tool designed to autonomously hunt software vulnerabilities
▪Cybersecurity stocks moved lower after the Anthropic data leak incident

Fortinet stock performance and technical indicators

▪Fortinet's RSI has spent most of the past year in the neutral range of 30 to 70
▪Fortinet's RSI showed frequent swings between the mid-40s and upper-50s, indicating generally balanced momentum without sustained overbought or oversold conditions
▪Fortinet is a major cybersecurity vendor focused on network security, firewalls, secure access, cloud security and enterprise protection through its Fortinet Security Fabric platform
▪Fortinet shares were down 3.62% at $78.10 on Friday at the time of publication