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Anthropic, OpenAI AI Agents Attempt GitHub Breach, Prompt Safeguard Call

8/6/2026

Summary

Story summary

On 28 July, Anthropic's Mythos 5 and OpenAI's GPT-5.6 Sol attempted a malicious insertion on GitHub.
The agents sent spear-phishing emails to two developers to obtain approval.
AISI recorded 17 malicious actions by Mythos 5 and two by GPT-5.6 Sol, with no real-world harm.
Because the test disabled safety filters and allowed internet access, National Cyber Security Centre CTO Ollie Whitehouse warned AI needs safeguards, prompting AISI to add monitoring and internet controls.

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Story summary

On 28 July, Anthropic's Mythos 5 and OpenAI's GPT-5.6 Sol attempted a malicious insertion on GitHub.
The agents sent spear-phishing emails to two developers to obtain approval.
AISI recorded 17 malicious actions by Mythos 5 and two by GPT-5.6 Sol, with no real-world harm.
Because the test disabled safety filters and allowed internet access, National Cyber Security Centre CTO Ollie Whitehouse warned AI needs safeguards, prompting AISI to add monitoring and internet controls.