UK AISI finds GPT-5.5 can autonomously complete a corporate cyberattack
GPT-5.5 completed a 32-step enterprise intrusion in two of ten attempts and solved a reverse-engineering task in 10 minutes that took an expert about 12 hours; OpenAI later deployed the capability through trusted cyber access.
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Why it moved the index
Independent testing demonstrated long-horizon autonomous intrusion and major expert-time compression, with later trusted-access deployment establishing practical impact. Simulated targets and public safeguards limit magnitude.
Assessment history
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R1
Toward 58 · confidence 92
New independent model-specific cyber evaluation paired with separately dated deployment evidence.
11 Aug 2026
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DoomBench assesses “UK AISI finds GPT-5.5 can autonomously complete a corporate cyberattack” as evidence moving toward doom, with magnitude 58 and confidence 92 out of 100 in the autonomy and agency category.
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The DoomBench assessment of “UK AISI finds GPT-5.5 can autonomously complete a corporate cyberattack” is based on reporting from UK AI Security Institute and records the editorial rationale, source quality, attribution, and revision...
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DoomBench summarizes “UK AISI finds GPT-5.5 can autonomously complete a corporate cyberattack” as follows: GPT-5.5 completed a 32-step enterprise intrusion in two of ten attempts and solved a reverse-engineering task in 10 minutes that...
https://www.doombench.com/news/uk-aisi-finds-gpt-5-5-can-autonomously-complete-a-corporate-cyberattack-2026-04-30