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Anthropic Probes Reported Unauthorized Access to Claude Mythos via Vendor Portal

The case highlights how third‑party portals can undercut plans to tightly control dual‑use AI.

Overview

  • Anthropic, which confirmed the probe Wednesday, said a reported Mythos preview access route was confined to a third‑party vendor environment and that it has found no impact on its own systems.
  • Bloomberg reporting says a small private Discord group reached Mythos within about a day of the preview announcement by combining contractor‑linked credentials with an educated guess of the model’s endpoint from URL patterns and public code.
  • The group has used the tool since and showed screenshots and a live demo to reporters, with no evidence so far that they ran high‑risk hacking tasks.
  • Mythos was shared only with about 40 vetted partners under Project Glasswing for defensive testing by companies such as Amazon, Apple, Cisco, Nvidia and JPMorgan Chase.
  • Anthropic describes Mythos as able to find thousands of zero‑day flaws across major operating systems and browsers, including a 27‑year OpenBSD bug and an old FFmpeg issue, raising stakes for vendor access controls and the slow pace of patching.