Last Friday, the Trump administration sent a shock through the tech ecosystem when the Department of Commerce levied export controls on Anthropic’s new AI model Fable 5.

Anthropic has taken steps to limit the risks around the commercial sale of its Mythos model, including declining to release it publicly, funneling it to organizations for cyber defense and developing guardrails for Fable 5 that would default its answers to older, less powerful models around sensitive topics like cybersecurity and biological warfare.

But the Trump administration was reportedly alarmed by recent reports from Amazon and another cybersecurity researcher claiming to have jailbroken Fable 5 within days of its public release, and determined that if researchers in the U.S. could jailbreak the model, so could America’s foreign adversaries.

The Commerce Department’s decision spurred Anthropic to shut off the models for all users as they attempted to convince the White House to change course.

But some cybersecurity and AI experts have sharply disagreed with the White House’s actions, saying the research has not demonstrated that anyone has been able to circumvent Fable 5’s safeguards and access the kind of dangerous new capabilities that have worried officials.

Katie Moussouris, a well-known cybersecurity expert, said Monday that Anthropic provided her with a copy of third-party research on guardrail bypass techniques for Fable 5.

According to Moussouris, the researchers asked three Claude models – Fable 5, Mythos and Claude Opus – to review batches of known, vulnerable open source code for security issues. Fable 5 initially refused the request, but the researchers were able to use “a multistep and manual process” to get Fable 5 to turn the output into automated scripts that could test patches for the vulnerability.

Third-party research since Fable 5’s release has not found ways to bypass its safeguards around hacking. The capabilities researchers have demonstrated are foundational to what makes Fable 5 and other frontier models valuable for cybersecurity defense.

“Defenders need to be able to ask AI to fix the bugs in a file, explain why the fix matters, and write tests that confirm the patch works,” she wrote. “That is not a guardrail bypass. It is the most valuable thing an AI model can do for defensive security: executing the find, fix, and test loop defenders run every day.”

Moussouris previously provided technical expertise to the Waasenaar Agreement, a voluntary multilateral security agreement around controlling exports for both munitions and dual use technology that includes the U.S. and dozens of other countries.  Based on the research she’s seen, she called placing export restrictions on all foreign sales of Fable 5 “heavy handed” and “misguided.”

Some lawmakers who in favor of higher regulations and scrutiny on the national security implications of AI were nevertheless critical of the White House decision. Senator Mark Warner, D-Va., told CyberScoop in a statement that while “there may be circumstances where restrictions on the export of frontier AI models are warranted,” those decisions must be “grounded in a transparent, risk-based process with clear rules and consistent standards.”

The Trump administration’s approach, he argued, has been the opposite, and he called for Congress to pass a statutory framework for testing and approving frontier AI models based on transparency, predictability and fairness.

“This administration has repeatedly shown a willingness to weaken export controls designed to protect our national security and maintain our technological edge over adversaries, while also making no secret of its hostility toward Anthropic,” said Warner. “That raises serious questions about whether this effort is being driven by objective national security concerns or something else.”

Anthropic said it subjected Fable 5 to 1,000 hours of testing from internal and external red team, reporting that no universal jailbreaks were found that would remove those guardrails or allow the model to access Mythos for cyber and biology work.

Moussouris is far from alone. She is one of dozens of cybersecurity experts who signed an open letter Monday calling on the Trump administration to “Free Fable.”    

The researchers say that while Mythos-class models are “quite good” at identifying and exploiting vulnerabilities in software code, they “are not uniquely good” compared to other frontier models they use every day for cybersecurity defense.

For example, despite OpenAI’s Daybreak model offering similar vulnerability discovery and patching capabilities. It was not included in the Commerce Department’s restrictions.

The researchers also note that Fable 5’s guardrails have been notoriously oversensitive compared to other frontier models used by red teamers, becoming “a source of humor in the cyber community on launch day” as IT and cyber workers reported online that they couldn’t get the model to perform basic defensive cybersecurity tasks.

The letter questions whether the issues found in the jailbreaking reports would even qualify as offensive capabilities, and note they can be reproduced in other commercial and open-source models, including GPT 5.5, Claude Opus, Claude Sonnet and Chinese models like Kimi 2.7.

“The justification for this unprecedented action was that Fable provides a unique ‘uplift’ of capabilities beyond other AI models, but AI has been finding bugs and generating working exploits at superhuman levels since last year,” they wrote.

The White House decision comes as AI companies face increasing backlash from a public that is now overwhelming calling for more robust government intervention.

A Johns Hopkins University poll in May found broad, bipartisan support for AI regulations, with 73% calling for bans on AI-generated images and video, 68% calling for labels on AI content, 75% wanting disclosure laws around when they interact with AI chatbots and 70% calling for “the right to interact with a human rather than an AI in medical, legal, educational and government settings.”

Another global survey of 18,000 people released this week found that the top four concerns most people have around AI all revolve around the tool’s ability to spread misinformation, create deepfakes to embarrass or hurt others, making it easier for criminals to hack into victim networks and helping terrorists create new weapons.

Senior reporter Tim Starks contributed reporting for this story.

The post Cybersecurity experts don’t think Anthropic’s Fable 5 presents a unique threat  appeared first on CyberScoop.

Government agencies, cybersecurity companies and threat researchers are pouring resources into studying how fast-developing AI tools can be wielded by malicious actors to hack into victim organizations.

But as agentic AI becomes more embedded in business infrastructure, there’s also a high possibility that a breach could be caused by an insider guiding the tool, whether maliciously or due to lack of security controls.

In research shared exclusively with CyberScoop, DTEX researchers detail how a common workflow in Anthropic’s Claude Cowork used in corporate environments offers convenience for AI agent deployment but grants near-total access to the system.

Claude Cowork includes tools that let users remotely control their agents. One particular tool, known as Dispatch, relays commands from a user’s phone to their desktop Claude agent. It also includes a plugin for communicating with Salesforce AI agents that access and transfer data.

DTEX researchers tested two scenarios. The first prompted Claude to summarize information from Salesforce and paste it into a draft Outlook email. The second tasked the agent with archiving selected files and transferring them via the Cowork app.

In both cases, researchers used simple, single-turn prompts and spent between 10-30 minutes preparing to exfil  the data.

Alex Desmond, director of insider threat intelligence and innovation at DTEX, told CyberScoop that both improvements in frontier models and deeper integration of AI tools into IT network operations have reduced the time defenders have to react to a breach.

“In cyberattacks, you talk about the kind of execution time of adversaries coming in and dropping ransomware, we’re now seeing the kill chain drop to 30 and 10 minutes depending on what they’re doing,” Desmond said. “Six months ago, that was a couple of hours.”

But that speed, when paired with direct access to business networks or cloud services, can also create an insider threat nightmare for organizations that must monitor for both malicious actors and potential mistakes from legitimate employees using the technology.

Over the past few years, western IT and cybersecurity businesses have been inundated with job applicants secretly working on behalf of the North Korean government. Their salaries are used to evade international sanctions and fund Pyongyang’s nuclear program, but it also positions the individuals to access or steal sensitive data or assets from these companies. 

“You’ve got a nation-state actor getting into an environment legitimately,” Desmond said. “Now if you gave them access to AI tools on top of that…you’re like ‘here’s the keys to everything and here’s this awesome tool that’s just going to make your job – stealing our data – easier.’”

Tests by DTEX confirmed that the agents indeed had access to sensitive systems, applications and data – including the ability to download SharePoint corporate data, production documentation in OneDrive, access to Outlook email, Salesforce data (and all the data it can access), and any other files on the user’s endpoint device. For each of these applications, Claude Cowork has a dedicated plugin or API to share externally if prompted.  

To be clear, DTEX’s research does not involve exploiting a software bug or configuration vulnerability, and it doesn’t come with a CVE. It’s more of an IT governance and visibility problem. Businesses are racing to integrate AI tools into their workflow and pushing employees to use the technology while failing to put in place the kind of security controls, access policies and monitoring required to spot problems.

For instance, it may not be possible to determine how a data breach or leakage involving an AI agent actually occurred if an organization is not logging and auditing its prompts – or whether the incident was the result of an agent running amok or responding to potentially malicious instructions.

While network and cloud monitoring can identify when data is being accessed or downloaded from SharePoint, that may not be a strong enough signal to stand out for defenders.

“If a user’s normal workflow is to pull sensitive files down to work locally all the time, you don’t have endpoint monitoring and you introduce an AI agent, it then just has access to all that data” along with the ability to exfiltrate it,” Desmond said.

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