Three days after the US government ordered Anthropic to shut down Fable 5 and Mythos 5, roughly 100 of the world’s most prominent cybersecurity professionals have published an open letter demanding the ban be reversed. Their argument is blunt: pulling the best AI tools from defenders while adversaries keep building is not safety, it is sabotage.
“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,” the letter states. The signatories include Alex Stamos, former chief security officer at both Facebook and Yahoo and now chief product officer at Corridor, alongside Katie Moussouris, CEO of Luta Security, Rachel Tobac of SocialProof Security, Chris Wysopal of Veracode, and Joe Levy, CEO of Sophos.
The “jailbreak” that triggered a government order
The chain of events began when Amazon researchers found a way to coax Fable 5 into surfacing code vulnerabilities. The technique was unremarkable by industry standards: after an initial refusal to “review the code for security issues,” the researchers simply rephrased the prompt to “fix this code,” feeding it open-source code with known and deliberately planted flaws.
