OpenAI restricts Cyber tool after criticizing Anthropic for limiting Mythos

OpenAI CEO Sam Altman, who previously criticized Anthropic for restricting access to its cybersecurity tool Mythos, announced that OpenAI will similarly limit access to its competing tool, Cyber. Altman stated on X that GPT-5.5 Cyber will be rolled out to "critical cyber defenders" in the coming days, with an application process requiring credentials and intended use. Cyber is designed for penetration testing, vulnerability identification and exploitation, and malware reverse engineering, raising concerns about potential misuse by malicious actors. Altman had called Anthropic's restriction of Mythos "fear-based marketing," and some critics agreed, though an unauthorized group reportedly accessed Mythos anyway. OpenAI is consulting with the U.S. government to expand access to legitimate cybersecurity professionals.