Evaluation of Prompt Injection Defenses in Large Language Models
LLM-powered applications routinely embed secrets in system prompts, yet models can be tricked into revealing them. We built an adaptive attacker that evolves its strategies over hundreds of rounds and tested it against nine defense configurations across more than 20,000 attacks. Every defense that relied on the model to protect itself eventually broke. The only defense that held was output filtering, which checks the model's responses via hardcoded rules in separate application code before they reach the user, achieving zero leaks across 15,000 attacks. These results demonstrate that security boundaries must be enforced in application code, not by the model being attacked. Until such defe...
| Authors | Priyal Deep, Shane Emmons, Amy Fox et al. |
|---|---|
| Primary category | cs.CR |
| Published | 26 April 2026 |
| Last updated at source | 12 May 2026 |
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