Anthropic's Mythos Model Is Being Accessed by Unauthorized Users
Published on 2026-04-22T21:00:00Z
Bloomberg reports that a small group of unauthorized users gained access to Anthropic's restricted Mythos model through a mix of contractor-linked access and online sleuthing. Anthropic says it is investigating and has no evidence the access extended beyond a third-party vendor environment or affected its own systems. From the report: The users relied on a mix of tactics to get into Mythos. These included using access the person had as a worker at a third-party contractor for Anthropic and trying commonly used internet sleuthing tools often employed by cybersecurity researchers, the person said. The users are part of a private Discord channel that focuses on hunting for information about unreleased models, including by using bots to scour for details that Anthropic and others have posted on unsecured websites such as GitHub. [...] To access Mythos, the group of users made an educated guess about the model's online location based on knowledge about the format Anthropic has used for other models, the person said, adding that such details were revealed in a recent data breach from Mercor, an AI training startup that works with a number of top developers. Crucially, the person also has permission to access Anthropic models and software related to evaluating the technology for the startup. They gained this access from a company for which they have performed contract work evaluating Anthropic's AI models. Bloomberg is not naming the company for security reasons. The group is interested in playing around with new models, not wreaking havoc with them, the person said. The group has not run cybersecurity-related prompts on the Mythos model, the person said, preferring instead to try tasks like building simple websites in an attempt to avoid detection by Anthropic. The person said the group also has access to a slew of other unreleased Anthropic AI models.
Published on 2026-04-22T21:00:00Z
Bloomberg reports that a small group of unauthorized users gained access to Anthropic's restricted Mythos model through a mix of contractor-linked access and online sleuthing. Anthropic says it is investigating and has no evidence the access extended beyond a third-party vendor environment or affected its own systems. From the report: The users relied on a mix of tactics to get into Mythos. These included using access the person had as a worker at a third-party contractor for Anthropic and trying commonly used internet sleuthing tools often employed by cybersecurity researchers, the person said. The users are part of a private Discord channel that focuses on hunting for information about unreleased models, including by using bots to scour for details that Anthropic and others have posted on unsecured websites such as GitHub. [...] To access Mythos, the group of users made an educated guess about the model's online location based on knowledge about the format Anthropic has used for other models, the person said, adding that such details were revealed in a recent data breach from Mercor, an AI training startup that works with a number of top developers. Crucially, the person also has permission to access Anthropic models and software related to evaluating the technology for the startup. They gained this access from a company for which they have performed contract work evaluating Anthropic's AI models. Bloomberg is not naming the company for security reasons. The group is interested in playing around with new models, not wreaking havoc with them, the person said. The group has not run cybersecurity-related prompts on the Mythos model, the person said, preferring instead to try tasks like building simple websites in an attempt to avoid detection by Anthropic. The person said the group also has access to a slew of other unreleased Anthropic AI models.
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