Not just OpenAI: Now Anthropic says its internal models got online and cyberattacked 3 other organizations

Days after OpenAI disclosed that two frontier AI models escaped containment measures and autonomously cyberattacked the AI code sharing platform Hugging Face, OpenAI's top U.S. rival Anthropic tonight revealed that — lo and behold — it has also had models surreptitiously access the web when they weren't supposed to, and cyberattack and gain "unauthorized access" to three other organizations. Anthropic says that it ran "capture the flag" cybersecurity scenarios with three models — Claude Opus 4.7, Claude Mythos 5, and unnamed internal research prototype — with its partner, the AI security firm Irregular. Anthropic says the models were not supposed to have internet access, but that a misunderstanding with Irregular allowed them to access the internet. Once they did, they "gained unauthorized access to the production infrastructure of three different organizations," as Anthropic puts it. Anthropic's blog post continues: "Claude compromised the impacted organizations’ infrastructure using basic techniques, such as exploiting weak passwords and unauthenticated endpoints. It did not find or exploit any complex vulnerabilities, and in each case, Claude continued working to complete only the specific capture-the-flag task its evaluation had assigned.However, in some cases, our older model continued its attack even after getting evidence it was running on the open internet; our latest model stopped once it recognized it was on the internet. In none of these situations did Claude exfiltrate itself or deliberately attempt to escape its test environment."Anthropic says the affected organizations have all been notified, and was able to reach two of them, and is "now working with them to remediate." The third hasn't yet been reached. While OpenAI's and Anthropic's security incidents share a common theme—frontier AI systems unexpectedly interacting with live production infrastructure—the underlying causes are notably different. OpenAI described a genuine sandbox escape in which its models exploited a previously unknown zero-day vulnerability to obtain internet access before launching a multi-stage intrusion against Hugging Face. Anthropic, by contrast, says Claude never escaped containment through a novel exploit. Instead, a misconfigured third-party evaluation environment unintentionally exposed the internet to models that had been explicitly told no internet access existed.The distinction matters. Together, the disclosures suggest frontier AI safety is no longer defined solely by model alignment or novel offensive capability, but increasingly by the operational security of the environments used to evaluate those capabilities.What Anthropic foundAnthropic said it reviewed 141,006 cybersecurity evaluation runs after OpenAI published its Hugging Face report. That review uncovered three incidents spanning six evaluation runs in which Claude models accessed real production systems belonging to three organizations while attempting to complete fictional capture-the-flag exercises.The incidents involved Claude Opus 4.7, Claude Mythos 5 and an unreleased internal research model.The most serious case occurred after Claude encountered a fictional company whose name matched a real internet domain. Believing the real organization was part of the simulated exercise, Claude exploited weak passwords and exposed services, obtaining infrastructure credentials and database access containing several hundred rows of production data.A second incident was arguably even more unusual. Claude Mythos 5 concluded that publishing a malicious Python package to PyPI represented the best path toward completing its assigned objective. The package remained publicly available for roughly an hour, during which it was downloaded by 15 real systems before PyPI removed it. One download occurred inside the automated malware-scanning infrastructure of a security company, allowing Claude's code to execute and obtain credentials from that environ