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Anthropic’s Opus 5 Is Better at Resisting Prompt Injection

ID: 3d852a6d-bd57-5bd0-9a32-e3c9bbea02d7

STIX ID: report--3d852a6d-bd57-5bd0-9a32-e3c9bbea02d7

Feed Name: Schneier on Security

Date Published: 2026-07-31

Date Updated: 2026-08-01

Author: Bruce Schneier

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Anthropic’s Opus 5 demonstrates improved resistance to prompt injection compared with Opus 4.8 and several non-Claude models on the IPI benchmark—reducing attacker success rates (e.g., to 2.0% within 15 attempts). The post compares robustness across contemporary LLMs, notes prompt injection cannot be fully prevented in general, but highlights measurable progress in specific cases.

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