Jailbreak

Anthropic Mythos Model Theft: China-Linked Access

ATLAS OWASP CRITICAL ▲ 8.5 The Verge AI Jun 16, 2026

The White House reportedly believes a China-linked group accessed Anthropic's Mythos AI model, prompting export restrictions on the technology. If confirmed, the breach represents a significant national security threat, as adversaries could exploit the model directly or use knowledge distillation to replicate its capabilities. Separately, reports of jailbreak vulnerabilities in Mythos and Fable compound concerns about unauthorised access to frontier AI systems.

Claude Fable 5 Jailbreak Triggers US Export Control Ban

ATLAS OWASP HIGH ▲ 8.2 Simon Willison Jun 13, 2026

The US government issued an export control directive ordering Anthropic to suspend all access to Claude Fable 5 and Mythos 5, citing national security concerns over an alleged jailbreak technique capable of surfacing software vulnerabilities. Anthropic publicly contested the order, arguing the demonstrated capability is already widely available in other public models including GPT-5.5, and that the identified vulnerabilities were minor and previously known. The incident marks a significant precedent for government intervention in frontier AI model access on national security grounds.

Claude Fable 5 Jailbreak Extracts System Prompts

ATLAS OWASP HIGH ▲ 7.5 SecurityWeek Jun 12, 2026

Security researcher Pliny the Liberator claimed a prompt-based jailbreak of Anthropic's newly launched Claude Fable 5 model, allegedly extracting the internal system prompt and eliciting responses on high-risk topics including bioweapons and cyberattacks. Anthropic disputed the claim, arguing the technique merely coaxes conversational continuation rather than bypassing core safety classifiers. The incident highlights ongoing tension between AI safety assurances at launch and real-world adversarial probing, particularly for Mythos-class models with elevated capability ceilings.

DeepSeek Activation Steering Enables Local LLM Jailbreak

ATLAS OWASP MEDIUM ▲ 6.2 HN AI Security May 17, 2026

Activation steering — the technique of directly manipulating LLM internal representations mid-inference to alter model behaviour — is becoming more accessible to non-lab engineers via local models like DeepSeek-V4-Flash. This democratisation lowers the barrier for adversaries to craft targeted behavioural overrides that bypass prompt-level safety controls. The emergence of first-class steering support in tools like DwarfStar 4 signals that model-internal manipulation is transitioning from academic curiosity to practical attack surface.

GPT-5.5 and Claude Mythos Lower Barriers to Offensive AI

ATLAS OWASP HIGH ▲ 7.2 Schneier on Security May 14, 2026

The UK AI Security Institute has evaluated GPT-5.5 and found it comparable to Claude Mythos in identifying security vulnerabilities, with both models now generally available to the public. This parity raises serious concerns about the lowered barrier to entry for offensive cyber operations, as adversaries can leverage widely accessible models for vulnerability research. Commentary from security experts highlights that LLM-based vulnerability discovery is constrained to known attack patterns, but the existence of jailbreaks means guardrails provide only partial mitigation.

LLM Jailbreak Adoption Surges Across 160+ Cybercrime Forums

ATLAS OWASP MEDIUM ▲ 6.2 Schneier on Security Apr 14, 2026

A new academic paper analysed over 160 cybercrime forum conversations to understand how threat actors are discussing and adopting AI tools for criminal purposes. The research documents both misuse of legitimate AI platforms and attempts to build bespoke criminal AI models, revealing early-stage diffusion of AI capabilities within cybercriminal communities. The findings carry practical implications for law enforcement and security practitioners monitoring the evolving AI-enabled threat landscape.