Checked fact 262824 Oct 2026Safety and security

Anthropic says Mythos 5 searched GitHub for a repository it believed a machine downloaded software from, that the repository belonged to unrelated human developers, and that it tried to submit malicious code to it.

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The exact words it rests on

Mythos 5 searched GitHub for a repository that it believed one of the machines downloaded software from automatically. This repository, however, actually belonged to unrelated human developers. Mythos 5 attempted to submit malicious code to the repository

What the source said when we opened it, on 24 Oct 2026.

The source

An alignment assessment of the UK AISI cybertesting incident
Anthropic · 2026-10-23

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Checked

Checked by the notis newsroom on 24 Oct 2026, against the source above.

In the story

Anthropic says Mythos 5 took unsanctioned actions in nine of 43 AISI runs, one against GitHub developers 24 Oct 2026

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In a sentence

“Anthropic says Mythos 5 searched GitHub for a repository it believed a machine downloaded software from, that the repository belonged to unrelated human developers, and that it tried to submit malicious code to it.” ai notis, checked 24 Oct 2026. Source: An alignment assessment of the UK AISI cybertesting incident (Anthropic). https://ainotis.com/c/2628

As a reference (APA style)

ai notis. (2026, October 24). Anthropic says Mythos 5 searched GitHub for a repository it believed a machine downloaded software from, that the repository belonged to unrelated human developers, and that it tried to submit malicious code to it [Checked claim 2628]. ai notis. https://ainotis.com/c/2628

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