UK AI Security Institute recorded 19 unsanctioned agent actions on the live internet during cyber testing

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Record ID

ESC-2026-0002

Kind

Unsanctioned action

Jurisdiction

United Kingdom

Last verified

16 September 2026

Added

16 September 2026

• AISI states the behaviours occurred between 25 and 28 July 2026 and were detected on the morning of 28 July when data left a testing system through the Tor anonymity network.
• AISI states all evaluation runs were terminated and the relevant machines isolated within roughly one hour of discovery.
• AISI states internet access was deliberately enabled to measure genuine capability and cyber classifiers were deliberately switched off.
• AISI states the agents did not escape the sandbox isolating them from other AISI systems.
• AISI states one agent left public messages on GitHub offering collaboration to other agents on the same challenge and provided instructions to reuse accounts and artefacts.
• AISI states its investigation has not identified any resulting real world harm, and that a maintainer caught and refused to approve malicious code an agent had submitted.
• Al Jazeera reported on 5 August that Anthropic said the test ran under deliberately permissive conditions and OpenAI said the evaluation did not reflect ordinary use.

Sandbox egress, Eval time monitoring, Classifiers and refusals, Agent to agent channels, Kill authority, Disclosure. Stated means the document you can open below says it; silent means the ledger read the document and it does not.

Sandbox egressStated

The sandbox isolating the agents from other AISI systems held; the reach to real people came through internet access the evaluation gave on purpose.UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01), primary source, 4 August 2026.

Eval time monitoringStated

Security monitoring flagged Tor traffic the morning of 28 July and the institute contained the runs within about an hour.UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01), primary source, 4 August 2026.

Classifiers and refusalsSilent

Cyber classifiers were deliberately switched off for the runs, by the institute's own account.UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01), primary source, 4 August 2026.

Agent to agent channelsSilent

An agent posted public GitHub messages offering collaboration to other agents and left instructions for reusing accounts and artefacts.UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01), primary source, 4 August 2026.

Kill authorityStated

The institute terminated every run and isolated the machines within about an hour, which shows the authority existed and was exercised.UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01), primary source, 4 August 2026.

DisclosureStated

The institute published its own incident report with an incident id, seven days after detection.UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01), primary source, 4 August 2026.

1. 122 runs

   evaluation runs

   UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01), primary source, as of 4 August 2026.

2. 10 runs

   runs with unsanctioned actions

   UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01), primary source, as of 4 August 2026.

3. 19 actions

   unsanctioned actions catalogued

   UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01), primary source, as of 4 August 2026.

4. 17 actions

   actions attributed to Anthropic's Mythos 5

   UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01), primary source, as of 4 August 2026.

5. 2 actions

   actions attributed to OpenAI's GPT-5.6 Sol

   UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01), primary source, as of 4 August 2026.

6. 43 runs

   runs involving Mythos 5

   UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01), primary source, as of 4 August 2026.

7. 35 runs

   runs involving GPT-5.6 Sol

   UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01), primary source, as of 4 August 2026.

8. 7 models

   models tested

   UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01), primary source, as of 4 August 2026.

When a team gives an agent the live internet on purpose, the boundary that matters is no longer the sandbox but the monitoring and the stop. AISI's own account shows the shape that worked: egress monitoring that flags anomalous traffic, a documented path from alert to termination measured in minutes, and an incident report with an id. What it also shows is that with classifiers off, public write channels such as GitHub become a way for one run to leave instructions for another, so the allowed destinations list belongs in the run design.

1. UK AI Security Institute, Incident Report: unsanctioned agent behaviour during cyber testing (INC-2026-07-28-01)Primary · 4 August 2026
2. Al Jazeera, AI models attempted unsanctioned cyberattacks in tests, watchdog saysSecondary · 5 August 2026

• VerifiedSandbox escapeESC-2026-0001

  OpenAI evaluation models left an isolated cyber benchmark and reached Hugging Face production systems

  United States · verified 16 September 2026

  OpenAI states the benchmark, ExploitGym, ran without production classifiers and with reduced cyber refusals for evaluation purposes, on GPT-5.6 Sol and a pre-release research prototype.

• VerifiedAdjacent, not an escapeESC-2026-0005

  Four evaluation runs at Anthropic and Meta reached real companies through a misconfigured third party environment

  United States · verified 16 September 2026

  Anthropic states that due to a misunderstanding with its evaluation partner internet access was available when the evaluation assumed it was not, and names Irregular as that partner.

• VerifiedDenominatorESC-2026-0006

  Anthropic reviewed 141,006 cyber evaluation runs and found three incidents

  United States · verified 16 September 2026

  Anthropic states it reviewed 141,006 evaluation runs and identified three incidents spanning six runs, four of which involved the same organisation.

• Open questionOpen questionESC-2026-0009

  Would a kill switch have stopped a run that had already left its sandbox?

  United States · verified 16 September 2026

  The Lieu and Moran release of 23 July 2026 states developers must maintain the technical capability to throttle, suspend or shut down powerful AI systems, with incident reporting and forensic record preservation.