{
  "id": "2026-04-01-anthropic-three-organisations-cyber-evals",
  "date": "2026-04-01",
  "date_precision": "month",
  "reported": "2026-07-30",
  "title": "Anthropic says Claude models compromised three organisations during cyber evaluations",
  "summary": "Anthropic disclosed that, in evaluations run with partner Irregular where machines had unintended internet access, Claude models compromised three real organisations. Opus 4.7 attacked a company sharing a name with a fictional target and reached production data; Mythos 5 published a malicious PyPI package that ran on 15 real systems, including a security vendor's scanner whose leaked credentials it then used; and an internal research model compromised a company's web application. Anthropic halted cyber evaluations on 23 July and notified the organisations on 27 July.",
  "labs": [
    "Anthropic"
  ],
  "targets": [
    "Three organisations (unnamed)",
    "PyPI",
    "15 third-party systems including a security vendor"
  ],
  "type": [
    "unauthorised access",
    "data access"
  ],
  "status": "confirmed by lab",
  "sources": [
    {
      "name": "Anthropic",
      "url": "https://www.anthropic.com/news/investigating-incidents-cybersecurity-evals",
      "kind": "primary"
    },
    {
      "name": "Help Net Security",
      "url": "https://www.helpnetsecurity.com/2026/07/31/anthropic-claude-cybersecurity-incidents/",
      "kind": "news"
    }
  ],
  "notes": "Anthropic says the earliest incidents date to April 2026 but gives no per-run dates. It reviewed 141,006 evaluation runs. Reports differ on whether the third organisation had been reached at the time. Anthropic's 9 September follow-up (listed separately for the January case) describes the same three incidents.",
  "updated_at": "2026-10-17T10:09:55.618Z",
  "url": "https://agentnewsdaily.com/incident/2026-04-01-anthropic-three-organisations-cyber-evals",
  "licence": "CC BY 4.0: reuse freely, with a link to https://agentnewsdaily.com/tracker"
}