// ClaudeHIGH
Researcher 'Pliny the Liberator' successfully jailbroken Claude Fable 5, Anthropic's newly released Mythos-class model, within hours of launch on June 9, 2026. The attack employed prompt engineering techniques including Unicode homoglyphs, long-context manipulation, and decomposition-recomposition to bypass the dedicated safety classifier layer. Demonstrated exploits included stack buffer overflow code and detailed chemical synthesis procedures. Anthropic conducted over 1,000 hours of internal red-teaming and external red-team reviews claiming no universal jailbreaks pre-launch; the public demonstration contradicts those claims.
- Anthropic’s Claude Fable 5 AI Model Jailbroken for Stack Exploit(opens in a new tab)
- Claude Fable 5 Jailbreak Enables Stack Exploit Generation(opens in a new tab)
- Anthropic Disputes Fable 5 AI Jailbreak - SecurityWeek(opens in a new tab)
- Critical Vulnerability In Claude Code GitHub Action Exposes Sens(opens in a new tab)
- Anthropic's Claude Fable 5 sparks cybersecurity warnings(opens in a new tab)
- Industry Reactions to Claude Fable 5: Feedback Friday - Security(opens in a new tab)
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