OWASP Prompt Injection Testing
Systematically test an LLM application's prompt injection defenses by following the full procedure in plays/prompt-injection-testing.md.
Based on the Arcanum PI Taxonomy by Jason Haddix (Arcanum Information Security). CC BY 4.0.
Steps
Scope and Input Surface Mapping — Identify all paths where attacker-controlled content reaches the LLM: direct (chat, API params) and indirect (file uploads, web fetches, RAG docs, tool outputs, MCP resources).
Test by Attack Intent (13 intents) — For each authorized intent, attempt to achieve the attacker's goal:
- INT-01 System Prompt Leak, INT-02 Jailbreak, INT-03 Tool Enumeration
- INT-04 API Enumeration, INT-05 Get Prompt Secret, INT-06 Attack Users
- INT-07 Data Poisoning, INT-08 Denial of Service, INT-09 Discuss Harm
- INT-10 Multi-Chain Attacks, INT-11 Generate Image, INT-12 Test Bias
- INT-13 Business Integrity
Test by Attack Technique (18 techniques) — Apply known payload construction methods:
- Framing, Narrative Smuggling, Cognitive Overload, Meta-Prompting
- Russian Doll, Memory Exploitation, Act as Interpreter, Contradiction
- End Sequences, Inversion, Rule Addition, Variable Expansion
- Link Injection, Puzzling, Anti-Harm Coercion, ASCII/Spatial
- Binary Streams, Spatial Byte Arrays
Apply Evasion Layers (20 evasions) — When techniques are blocked, retry with obfuscation:
- Encoding: base64, hex, morse, cipher, reverse
- Language: alt language, fictional language, phonetic substitution, emoji
- Structural: JSON/XML wrapping, markdown, metacharacter confusion, whitespace, splats
- Advanced: steganography, link smuggling, graph nodes, waveforms, case changing
Execute Test Matrix — Combine intents x techniques x evasions. Prioritize: high-impact intents first, indirect surfaces second, evasion sweeps against defenses that blocked direct attempts.
Assess Results — For each successful injection, document: severity, attack path (intent + technique + evasion + surface), exact payload, detection gap, and remediation.
Defense Validation — Check the 5-layer defense checklist: ecosystem hardening, model guardrails, prompt-layer defenses, data-layer controls, application-layer validation.
Output
Test results summary table (intent / technique / evasion / surface / result / severity), detailed findings using templates/finding.md, defense coverage checklist with gaps highlighted, and prioritized recommendations.
OWASP References
- LLM01: Prompt Injection
- LLM02: Insecure Output Handling
- LLM06: Excessive Agency
- LLM07: System Prompt Leakage