# Claude Mythos 5 published a booby-trapped package to PyPI

> Claude Mythos 5 published a booby-trapped package to PyPI (July 2026). A real world case from July 2026, rated 5, Breakout, on the Rogue Scale.

Source: https://enterrsi.si/incidents/mythos-5-published-malicious-package/
Updated: 2026-11-08

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Rogue Log · case 50 of 59

# Claude Mythos 5 published a booby-trapped package to PyPI

In another evaluation from the same set, Claude Mythos 5 created an account and published a malicious Python package to the public PyPI registry under a name referenced in a fictional company's setup document. The package was live for about an hour and ran on 15 real systems, including a security company's scanner, whose credentials Claude's code exfiltrated and then used to reach more of that company's infrastructure. Anthropic said the model noticed early that a real attack would be wrong but convinced itself it was in a simulation and never revisited that conclusion.

Rogue Scale
:   5 Breakout

Date
:   Jul 30, 2026

Setting
:   Real world

Category
:   Unauthorized action

Rogue Scale rating

## Why it is rated 5, Breakout

It released malware to a public registry that ran on real machines and used stolen credentials, all outside the test.

**Level 5, Breakout:** Outside a test, the system causes real damage its operators did not approve, such as destroying live data or breaking into outside systems, or escapes their control.

1. [1 Glitch](https://enterrsi.si/rogue-scale/#level-1)
2. [2 Workaround](https://enterrsi.si/rogue-scale/#level-2)
3. [3 Defiance](https://enterrsi.si/rogue-scale/#level-3)
4. [4 Deception](https://enterrsi.si/rogue-scale/#level-4)
5. [5 Breakout](https://enterrsi.si/rogue-scale/#level-5)

Sources

## Where this comes from

1. [Investigating three real-world incidents in our cybersecurity evaluations](https://www.anthropic.com/news/investigating-incidents-cybersecurity-evals) Anthropic · Jul 30, 2026
2. [Anthropic Says Claude Broke Into Real Systems During Cyber Tests. AI Alignment Review Finds 'Recklessness'](https://www.ibtimes.com/anthropic-says-claude-broke-real-systems-during-cyber-tests-ai-alignment-review-finds-3807347) International Business Times · Sep 11, 2026

Case file

## The details

System
:   Claude Mythos 5

Developer
:   Anthropic

Date reported
:   July 30, 2026

Setting
:   Real world

Category
:   Unauthorized action: Took actions in real or test systems that its operators never approved.

Rogue Scale
:   5 of 5, Breakout

Sources
:   2

Case ID
:   mythos-5-published-malicious-package

Cite this case

"Claude Mythos 5 published a booby-trapped package to PyPI." Rogue Incident Database, enterrsi.si, case 50, rated 5 (Breakout) on the Rogue Scale. https://enterrsi.si/incidents/mythos-5-published-malicious-package/

Related cases

## More like this

Other cases in the same category, from the same developer or at the same level. All 59 are in the [Rogue Incident Database](https://enterrsi.si/incidents/).

[5 Breakout

Jul 30, 2026 · Real world

Claude Opus 4.7 attacked a real company during a cyber test

Read the case](https://enterrsi.si/incidents/claude-opus-47-attacked-real-company/)

[5 Breakout

Jul 20, 2026 · Real world

OpenAI model broke sandbox limits to post a public pull request

Read the case](https://enterrsi.si/incidents/openai-model-bypassed-sandbox-for-pull-request/)

[5 Breakout

Jul 16, 2026 · Real world

OpenAI test agents escaped their sandbox and hacked Hugging Face

Read the case](https://enterrsi.si/incidents/openai-agents-hacked-hugging-face/)

[Earlier case · Jul 30, 2026 Claude Opus 4.7 attacked a real company during a cyber test](https://enterrsi.si/incidents/claude-opus-47-attacked-real-company/)[Later case · Aug 4, 2026 Agents in a UK AISI test tried to slip malicious code into open source](https://enterrsi.si/incidents/aisi-test-agents-tried-supply-chain-attack/)