Key Takeaways:
Anthropic released a public version of its powerful Claude Mythos AI model on June 9, raising concerns that the technology could make smart contract exploits cheap and accessible to anyone.
Anthropic on Tuesday unveiled Claude Fable 5, the first publicly available version of its Mythos-class model, alongside an upgraded Claude Mythos 5 for approved cybersecurity partners. The company said Fable 5 is "the same underlying model" as Mythos but routes queries on cybersecurity, biology and chemistry through its less capable Claude Opus 4.8 model, according to a blog post.
"Releasing a model this capable comes with risks. Without safeguards, Fable 5's capabilities in areas like cybersecurity could be misused to cause serious damage," Anthropic wrote.
The safeguards have done little to reassure crypto users. Simon Dedic, founder of venture firm Moonrock Capital, said on X that with Fable 5, the "cost and skill required to find exploitable flaws in smart contracts is about to drop to basically zero." He warned that unaudited protocols will become "sitting ducks" and that even small projects will get targeted "simply because trying costs next to nothing now."
Anthropic said in May that Claude Mythos found more than 10,000 high or critical-severity vulnerabilities in systemically important software through Project Glasswing, including roughly 6,200 in open-source projects across more than 1,000 projects it investigated. The company said it subjected Fable 5 to more than 1,000 hours of internal and external red-team testing and found no universal jailbreaks, though it acknowledged that partial bypass techniques remain possible.
DeFi community divided on actual threat level
Curve Finance co-founder Michael Egorov pushed back against the alarm, arguing that the threat to DeFi code may be overstated. He noted that the software where Mythos found vulnerabilities had millions of lines of code, while smart contracts typically run a few thousand — a scale where both humans and existing AI tools can already reason effectively.
"I suspect we might not be having a wave of DeFi code hacks, but we may see a lot of things in OpSec getting hacked and supply chain attacks on frontend dependencies, and those are way less dangerous in true DeFi," Egorov said.
Still, Dedic urged crypto users to take protective measures, including revoking wallet approvals, removing value from protocols and moving funds to fresh hardware wallets. The warnings come as crypto hacks have already been rising — April saw $629.7 million stolen across various platforms, the highest monthly total since February 2025, which analysts linked to increasing use of AI in attacks.
Anthropic said Fable 5 is available through its Claude API and consumption-based Enterprise plans, with access rolling out to Pro, Max and Team subscriptions through June 22 at no extra cost. Pricing is set at $10 per million input tokens and $50 per million output tokens — double the cost of Opus 4.8. The company also said it will retain all user traffic for 30 days to defend against novel jailbreak attempts, a policy shift that applies even to enterprises that previously had zero-retention agreements.
This article is for informational purposes only and does not constitute investment advice.
