Anthropic's Claude Fable 5 introduces advanced cyber tools with safety protocols, posing risks to DeFi, which has already suffered over $840 million in hacks this year.
By Shaurya Malwa|Edited by Sheldon Reback Jun 13, 2026, 6:00 p.m. 4 min readMake preferred on ShareShare this articleCopy linkX (Twitter)LinkedInFacebookEmailMake preferred on (Gerd Altmann/Pixabay)SummaryShow- Anthropic's Claude Fable 5 model enhances reasoning and coding skills while aiming to prevent harmful applications. A more robust Mythos 5 version is limited to approved security personnel.
- Experts caution that while advanced AI may not create new types of crypto hacks, it will significantly expedite the identification of vulnerabilities and the development of exploit methods, including social engineering and flawed signing processes.
- In 2026, DeFi has experienced over $840 million in losses, primarily due to human error rather than issues within smart contracts.
The latest AI model from Anthropic, which enhances reasoning and coding capabilities, arrives in a cryptocurrency landscape already troubled by security breaches, potentially worsening the situation.
On Tuesday, the company unveiled Claude Fable 5, a public iteration of its most powerful Mythos class model. This model comes in two variants: one for general access and another for restricted use.
The public version features enhanced reasoning and coding skills while attempting to block the most harmful applications. A less restricted version, Claude Mythos 5, is only available to approved users in the cybersecurity and critical infrastructure sectors.
Experts believe that Mythos can detect and link zero-day vulnerabilities, or unrecognized software flaws, and assist in converting a bug into an operational attack. According to Anthropic, the software aims to intercept potential attack vectors by identifying high-risk requests. Once flagged, these are directed to a less capable model, Claude Opus 4.8.
The company claims this fallback mechanism activates in under 5% of interactions. Furthermore, it highlighted in a blog post that specialized cybersecurity teams and over 1,000 hours of external bug-bounty efforts have not uncovered a universal method to compromise the system.
Nonetheless, Anthropic acknowledges that the system is not infallible, anticipating that persistent and well-resourced attackers will continue their efforts due to the value of such capabilities.
"The advantages of Mythos-level capabilities are appealing to many adversaries, such as those who could profit from cyberattacks, thus we anticipate they will be motivated to bypass our safety protocols," the firm stated in the post.
"... not a reliable control against a determined adversary."
However, identifying a target's weakness is not the most significant advancement AI offers to hackers. The true advantage lies in the unprecedented speed at which they can operate, and the limitations placed on AI models may not be sufficient to mitigate that speed.
The transition is less about AI creating new hacking techniques and more about the reduced time required to execute them, he explained. An advanced reasoning model can “diff every commit, grep every config, and enumerate every misconfiguration at machine speed,” referring to processes in software development.
The cryptocurrency sector is particularly vulnerable because software malfunctions can lead to immediate financial losses.
Social engineering
According to DefiLlama data, DeFi protocols lost over $840 million to hacks within the first five months of this year. April alone accounted for more than $600 million, marking the worst month on record for the decentralized finance sector.
However, the two most significant incidents were not straightforward smart-contract exploits that AI could facilitate.
In one case, a group linked to North Korea drained around $285 million from Drift Protocol following a six-month social engineering campaign that secured admin access. In another instance, an attacker took advantage of a single-verifier flaw, siphoning approximately $292 million from Kelp DAO.
Another recent event occurred on Tuesday, when Humanity Protocol, a decentralized human-identity service, lost over $30 million due to a private key compromise. CoinDesk discovered that a hacker accessed three out of six private keys stored on an employee's laptop.
This highlights a significant issue. While the most apparent smart-contract vulnerabilities may be the ones that Anthropic's filters are designed to catch, the largest losses have not required any bugs in contracts.
According to Guillemet from Ledger, the exploits stem from known vulnerabilities: social engineering, flawed signing processes, exposed keys, and human mistakes.
A model like Fable does not need to provide a complete exploit to alter the dynamics of an attack. It can analyze public repositories, compare previous software versions, summarize audit findings, and craft persuasive messages that exploit minor operational errors that humans overlook.
"These exploits remain rooted in social engineering and human error."
In such a setting, defenders must secure every key path, dependency, signing flow, and privileged account. With AI accelerating the reconnaissance phase, the importance of the final signing step increases. Private keys should be stored in a location inaccessible to compromised laptops, and users need a reliable interface that accurately displays what they are approving.
"Let's be clear: these exploits remain grounded in social engineering and human mistakes. AI did not create this situation; it merely made it more prominent and accelerated it to machine speed. The only true solution is a hardware root of trust: private keys generated and maintained on a certified secure element, with a trusted display for Clear Signing," Guillemet concluded.
A double-edged blade
Conversely, these same techniques can also be utilized to safeguard code. Pendle, a DeFi yield protocol, has employed Anthropic's models defensively since the initial version of Claude Opus. The team leverages AI to map its codebase and stress-test its contracts, including newly deployed ones. They assert that these tools identify bugs early and assist in producing cleaner code.
Pendle's developers noted in a Telegram interview that concerns around smart contracts are misplaced. A smart contract is concise, typically containing only about a dozen entry points. Skilled auditors have long been capable of comprehensively understanding a contract's state and testing every edge case.
"There are not that many lines of code in a smart contract to audit," the development team stated.
This suggests that the next significant crypto breach may not present as something novel. It will likely resemble previously seen issues, such as a compromised package, a deceived developer, or a flawed signing process that DeFi has already encountered.
What will change is that it is likely to occur sooner rather than later.
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