Just days after CEO Sam Altman slammed Anthropic for limiting access to its cybersecurity tool Mythos, OpenAI announced it will similarly restrict its own competing tool, GPT-5.5 Cyber, to a select group of "critical cyber defenders."
In a post on X Thursday, Altman revealed that OpenAI would begin rolling out Cyber to approved users in the coming days, with an application form on the company's website requiring credentials and planned use cases. The tool is designed for penetration testing, vulnerability identification and exploitation, and malware reverse engineering — capabilities that could be misused if they fell into the wrong hands.
Altman had previously criticized Anthropic's approach, calling it "fear-based marketing." Some industry observers agreed, suggesting Anthropic's rhetoric was overblown. The situation took an ironic turn when an unauthorized group reportedly gained access to Mythos despite the restrictions.
OpenAI stated it is working with the U.S. government to identify more legitimate cybersecurity users and expand access to Cyber in the future.