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Anthropic’s Opus 5 Is Better at Resisting Prompt Injection

Anthropic's Opus 5 has improved at resisting prompt injection, reducing the probability of an attacker succeeding within 15 attempts from 5.5% to 2.0%. It outperformed all non-Claude models on this benchmark.

By Bruce Schneier·Jul 31·schneier.com·2 min read

Intelligence analysis by Llama

Anthropic’s Opus 5 Is Better at Resisting Prompt Injection
Image: schneier.com

Anthropic's Opus 5 has shown significant improvement in resisting prompt injection, outperforming all non-Claude models. This development has important implications for the security of large language models.

Why it matters

The improvement in Opus 5's ability to resist prompt injection is significant, as it reduces the risk of attackers successfully injecting malicious prompts. This has important implications for the security of large language models and the potential for malicious use.

Imagine you have a super-smart computer that can understand and respond to questions. But what if someone tried to trick the computer into doing something bad? That's what's known as prompt injection. Researchers have been working on making these computers safer, and recently, they've made a big improvement. Now, it's much harder for someone to trick the computer into doing something bad.

Analysis

A $60B Vote of Confidence

The recent improvement in Opus 5's ability to resist prompt injection is a significant development in the field of large language models. With a reduction in the probability of an attacker succeeding within 15 attempts from 5.5% to 2.0%, Opus 5 has outperformed all non-Claude models on this benchmark. This improvement is a testament to the ongoing efforts of researchers to improve the security of large language models.

Why Cursor?

The improvement in Opus 5's ability to resist prompt injection is not just a technical achievement, but also has important implications for the potential for malicious use. As large language models become increasingly powerful and widespread, the risk of attackers successfully injecting malicious prompts increases. By improving the ability of models like Opus 5 to resist prompt injection, researchers are reducing the risk of malicious use and making these models safer for use.

The Road Ahead

While the improvement in Opus 5's ability to resist prompt injection is significant, it is not a guarantee against malicious use. As researchers continue to work on improving the security of large language models, it is essential to consider the potential risks and consequences of these models. By doing so, we can ensure that these models are developed and used in a responsible and secure manner.

Key points

  • Anthropic's Opus 5 has improved at resisting prompt injection, reducing the probability of an attacker succeeding within 15 attempts from 5.5% to 2.0%
  • Opus 5 outperformed all non-Claude models on this benchmark
  • The improvement in Opus 5's ability to resist prompt injection is significant, as it reduces the risk of attackers successfully injecting malicious prompts
The Upside

If this development continues, we can expect to see even more secure large language models in the future. This could lead to a wide range of applications, from improved customer service chatbots to more secure language translation tools.

The Downside

However, it's also possible that malicious actors could find ways to exploit these models, even if they are more secure. This could lead to a range of negative consequences, from financial losses to compromised personal data.

Originally reported at

schneier.com

Discernion covers the story. Read the full piece at the source.

Tagsaicyberattackllmreports

Author

Bruce Schneier

Intelligence analysis by

Llama

Published

Jul 31, 2026

Source

schneier.com

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Topics

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