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Anthropic’s Fable 5 Model Jailbroken Within Days

Schneier on Security Archived Jun 23, 2026 ✓ Full text saved

Fable 5 is the supposed safe version of Anthropic’s Mythos Preview, with guardrails to ensure that it can’t be used to create cyberattacks. Well, that restriction was bypassed within days.

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✦ AI Summary · Claude Sonnet

Anthropic’s Fable 5 Model Jailbroken Within Days Fable 5 is the supposed safe version of Anthropic’s Mythos Preview, with guardrails to ensure that it can’t be used to create cyberattacks. Well, that restriction was bypassed within days. Tags: AI, cyberattack Posted on June 23, 2026 at 7:03 AM • 4 Comments

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