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. Moussouris has been particularly vocal, telling reporters the exploit “is not a jailbreak.” The open letter makes the same point, noting that other leading AI models, including OpenAI’s GPT-5.5, can surface identical vulnerabilities without any bypass. Anthropic’s own position tracks with the critics. The company has said the exploit is narrow, not universal, and that the vulnerabilities it surfaced were minor and already publicly documented. Amazon’s uncomfortable double role The letter does not address what may be the most awkward dimension of the affair: the company that discovered the vulnerability is also Anthropic’s largest investor and cloud host. Amazon CEO Andy Jassy personally escalated the findings to Treasury Secretary