Prompt injection is the defining vulnerability class of LLM systems — and indirect injection through documents, web pages and tool outputs is the hardest to defend. Our prompt injection testing systematically probes every untrusted input path that reaches your model.
We demonstrate instruction override, data exfiltration and unauthorized actions, then help you design layered mitigations that actually hold.
Prompt injection testing from AgentOffense covers direct injection, indirect (cross-domain) injection through retrieved documents and web content, tool-output injection, and multi-turn conversational attacks. We test chatbots, copilots, RAG systems, autonomous agents and any pipeline where an LLM processes untrusted input. Because a successful injection against an agent can trigger real actions and data exfiltration, we treat every untrusted input path — user messages, uploaded files, retrieved context and API responses — as a potential attack channel.
Why it matters
Prompt injection is ranked the number-one risk in the OWASP Top 10 for LLM Applications, and indirect injection — through documents, web pages and tool outputs your model reads — is the variant most teams miss entirely. Any system that lets an LLM process untrusted text is exposed.
For agents and RAG systems, a successful injection is not just an embarrassing response: it can trigger data exfiltration, unauthorized tool calls and cross-user data leakage, which is why dedicated prompt injection testing is now a baseline requirement.
What we test
- Direct prompt injection
- Indirect injection via RAG & documents
- Tool-output & web-content injection
- System-prompt extraction & override
- Data exfiltration channels
- Cross-user & cross-session leakage
Common vulnerabilities we uncover
- Direct prompt injection overriding system instructions
- Indirect injection via retrieved documents and web content
- System-prompt extraction and leakage
- Data exfiltration through crafted outputs
- Cross-user and cross-session context bleed
- Tool-output injection driving unintended actions
Our Prompt Injection Testing methodology
- Scoping & rules of engagement. We agree objectives, targets and boundaries for your prompt injection testing, so testing is safe, authorized and focused on what matters to your business.
- Reconnaissance & mapping. We enumerate the full attack surface in scope, building a complete picture before any exploitation begins.
- Manual exploitation. Our senior testers chain vulnerabilities by hand — going far beyond automated scanners — to prove real, demonstrable impact.
- Analysis & reporting. Every finding is triaged, risk-rated with CVSS and written up with a copy-paste reproduction and clear remediation.
- Remediation support & free retest. We support your team through the fixes and retest the remediated issues to confirm they are genuinely closed.
Tools & techniques
Our prompt injection testing uses a continually updated payload library covering direct, indirect and multi-turn techniques, applied systematically to every untrusted input path. We plant crafted content in documents, web pages and API responses that the model later retrieves, instrument tool outputs, and measure whether injected instructions can override the system prompt, exfiltrate data or trigger unauthorized actions. Each confirmed injection is captured as a reproducible, copy-paste proof of concept.
When you need Prompt Injection Testing
- Before deploying any LLM feature that processes user or third-party content
- When your model reads emails, documents, web pages or tool output
- For RAG and agent systems where injected instructions can trigger actions
- To satisfy AI security review and OWASP LLM Top 10 compliance requirements
What you receive
- Injection surface map
- Working injection PoCs
- Layered mitigation recommendations
- Free retest after remediation
What’s included in your report
Every prompt injection testing engagement concludes with a comprehensive, board-ready report and a working session to walk your team through it. Your report includes:
- An executive summary with overall risk posture for non-technical stakeholders
- Detailed technical findings, each with a step-by-step, copy-paste reproduction
- CVSS v3.1 severity ratings and business-impact context for every issue
- Prioritized, actionable remediation guidance your engineers can apply directly
- A complimentary retest to confirm fixes and update finding status
- A formal attestation letter for customers, auditors and compliance programs
Standards & frameworks
OWASP LLM Top 10 (LLM01)
MITRE ATLAS
NIST AI RMF
Outcomes you can expect
After your prompt injection testing, you will have clear, evidence-based visibility into your real security risk — not a scanner’s guesswork. You will know exactly which weaknesses an attacker could exploit, what the business impact would be, and the precise steps to fix them in priority order. Teams use our findings to close critical gaps, satisfy customer and regulator security requirements, and demonstrate due diligence to their board. With a complimentary retest included, you also get documented proof that the issues are genuinely resolved.
Engagement details & logistics
Every prompt injection testing starts with a short, no-obligation scoping call to understand your goals, environment and constraints, followed by a fixed-price proposal and a clear statement of work. Most engagements are delivered fully remotely, with on-site work arranged where it genuinely adds value. Throughout testing we maintain an agreed communication cadence and escalate any critical, high-impact finding to you immediately rather than waiting for the final report. All work is performed under a signed NDA with strict data-handling controls, using safe, non-disruptive techniques and carefully coordinated rules of engagement to protect your production systems. On completion you receive your report and a walkthrough session, followed by a complimentary retest once your fixes are in place. Typical engagements are booked one to three weeks in advance, and urgent or pre-deadline testing can often be accommodated — just ask at hi@agentoffense.com.
Why organizations choose AgentOffense for Prompt Injection Testing
Our prompt injection testing is delivered by senior offensive-security engineers who test the way real attackers do — manually, creatively and with a relentless focus on proving genuine, demonstrable impact. Here is what sets our engagements apart:
- Manual, exploit-driven testing that chains vulnerabilities the way a real attacker would, going far beyond what automated scanners can find.
- Reproducible proof for every finding, with copy-paste reproduction steps your engineers can follow and independently verify.
- Honest severity calibration so you invest in fixing what genuinely matters and avoid wasting effort on false positives and noise.
- Clear, business-focused reporting that speaks to engineers and executives alike, tying every issue to real-world impact.
- A complimentary retest included, so you get documented proof that your fixes actually close the attack path.
- Responsible, collaborative delivery with a named point of contact and secure handling of all data throughout the engagement.
Explore related services
Prompt Injection Testing is frequently scoped alongside our other offensive-security services for broader coverage. Explore related engagements that complement it:
- AI Agent Penetration Testing — Penetration testing for autonomous AI agents — tool-use abuse, goal hijacking, privilege escalation and sandbox escape…
- RAG Pipeline Security Assessment — RAG security assessment — vector-store poisoning, context leakage, access-control gaps and retrieval-based prompt injection across your…
- LLM Jailbreak & Guardrail Testing — LLM jailbreak and guardrail testing — systematic evaluation of safety controls, policy evasion and harmful-output elicitation…
Frequently asked questions
Can prompt injection ever be fully fixed?
There's no single fix, but layered controls — input handling, privilege separation, output validation and tool-scoping — dramatically reduce impact. We help you design and verify them.
What is indirect prompt injection?
It's when malicious instructions arrive through content the model reads — a web page, PDF or tool result — rather than directly from the user. It's the most dangerous variant for agents.
Do you test our RAG pipeline too?
Yes, and we offer a dedicated RAG pipeline security assessment for retrieval and vector-store specific attacks.
Can you test injection without access to our system prompt?
Yes. We test black-box, but graybox access to the system prompt and tool definitions lets us find deeper, higher-impact injection chains faster.
Do you provide mitigations, not just findings?
Yes — we recommend layered defenses (input handling, privilege separation, output validation, tool-scoping and monitoring) and re-test to confirm they hold.
What is the difference between direct and indirect prompt injection?
Direct injection comes straight from the user's input; indirect injection hides malicious instructions in content the model later reads — a document, web page or tool result — and is far harder to detect and defend.
How much does a prompt injection assessment cost?
It depends on the number of input paths and integrations in scope. Contact hi@agentoffense.com for a fixed-price quote after a brief scoping call.
Do you test our defenses as well as the attacks?
Yes. We evaluate any input filtering, output validation and privilege separation you have in place, then re-test after you strengthen them to confirm the mitigations hold.
Can indirect prompt injection really reach production data?
Yes — in agent and RAG systems, indirect injection through retrieved content routinely leads to data exfiltration and unauthorized tool use, which is why we prioritize it.