Claude Fable 5 Doesn't Change the Mythos Security Story

Anthropic released frontier and consumer-safe versions of its Claude models—Mythos 5 and Fable 5—prompting discussion about their ability to discover and exploit software vulnerabilities. Anthropic implemented mitigations (Project Glasswing, safety classifiers, model switching to Opus 4.8) and external red-teaming, while security experts and the CSA recommend defenders focus on basics (segmentation, egress filtering, MFA, dependency management, automation) because the underlying risk—models lowering the bar for finding/exploiting vulnerabilities—remains even if no large-scale exploitation has been reported.