Cybersecurity Experts Pen Open Letter Opposing Fable 5 Ban Cybersecurity and AI safety are colliding in a high-stakes policy clash, as the U.S. government’s shutdown of Anthropic’s Fable 5 and Mythos 5 models faces a coordinated backlash from leading security professionals.

How the ban began

The controversy traces back to Amazon security researchers, who discovered they could prompt Fable 5 to surface software vulnerabilities by rephrasing requests, feeding the model open-source code with known and planted flaws. Their findings were escalated by Amazon CEO Andy Jassy to senior U.S. officials, triggering a directive three days ago ordering Anthropic to disable Fable 5 and Mythos 5 on national security grounds.

Security community pushes back

Within days, a loosely organized coalition of cybersecurity leaders — including CISOs, researchers, and executives from companies like Adobe, Zoom, Sophos and others — began drafting an open letter urging the Trump administration to reverse the restrictions. They argue that pulling Anthropic’s most advanced “Mythos-class” models “could kneecap cyber defenders just as they’re bracing for a wave of AI-powered hacking threats.”

By Monday, roughly 100 prominent experts had signed on, warning that “pulling the best AI tools from defenders while adversaries keep building is not safety, it is sabotage.” The letter argues that “this action has taken the best models away from defenders, created market uncertainty, and risked America’s AI leadership without any real risk to justify it.”

Competing views on risk

Critics emphasize that the exploit used to justify the ban “is not a jailbreak” and that other leading models, including foreign systems, can expose similar vulnerabilities without facing shutdowns. They say proof-of-concept exploits generated by Fable 5 can be “a blueprint” for attackers but are equally critical for defenders to understand and patch weaknesses.

Anthropic has echoed that the exploit is narrow and surfaces only minor, already public flaws, while the government has not publicly detailed its rationale. The unusual escalation path — from a major cloud provider that is also Anthropic’s largest investor directly to top officials — has further fueled debate over whether security, commercial rivalry, or both shaped the decision.

Continue reading https://foxvector.com/stories/019ed026-b03c-3e49-7186-2a4710eb5c4b