CREST-Certified AI and LLM Penetration Testing for UK Businesses
AI penetration testing for production LLM-powered applications, RAG pipelines, agent systems, and ML models. Aligned to the OWASP Top 10 for LLM Applications and NCSC AI Cyber Security Code of Practice. Manual exploitation of prompt injection, jailbreak, training-data poisoning, model theft, and excessive agency.
- Unlimited retesting
- Unlimited pre-retesting
- No hidden fees
“I would highly recommend EJN Labs to any organisation seeking reliable, detailed, and well-managed penetration testing services, particularly for government or enterprise-level projects.”
Imran SaghirProject Lead, SquareOne“There wasn’t another company we could find that could deliver what we needed in the timeframe we needed. The client loved it, and we got instant ROI from the engagement.”
Dan WilcocksonCo-Founder, CelloriPrompt injection (LLM01) tops the OWASP LLM Top 10, and automated scanners almost never catch it.
AI security is an emerging attack surface. We test it like a real attacker.
Modern AI applications (production chatbots, RAG-augmented assistants, autonomous agents, fine-tuned LLMs) introduce attack surfaces unfamiliar to traditional pen testing. Prompt injection bypasses guardrails. Training-data poisoning persists across model retraining cycles. RAG retrievers leak confidential data through clever query manipulation. Agentic systems with tool access can be coerced into destructive actions. Standard SAST / DAST tools cannot find these.
Our AI penetration testing is aligned to the OWASP Top 10 for LLM Applications, the NCSC AI Cyber Security Code of Practice, and the EU AI Act security obligations. Manual prompt-injection chains, jailbreak validation, training-data probe attacks, RAG retrieval manipulation, and agentic-system tool abuse, all delivered by CREST-certified testers with practical AI security experience.
ISO 42001, ISO 27001, SOC 2, and FCA AI risk reviews accept manual AI pen test evidence. Automated AI guardrail checks alone are generally insufficient.
OWASP LLM TOP 10 (2025)
What We Test in AI / LLM Penetration Testing
Manual exploitation of every OWASP LLM Top 10 (2025) risk across production LLM applications, RAG pipelines, agentic systems and ML models.
Prompt Injection
Direct and indirect prompt injection attacks that manipulate the LLM into ignoring its system prompt, leaking confidential information, or executing unauthorised tool calls.
Sensitive Information Disclosure
Unintended exposure of training data, system prompt, RAG corpus, or PII via cleverly-constructed queries. Membership inference attacks against model weights.
Supply Chain Vulnerabilities
Compromised model weights, tampered fine-tuning datasets, malicious LoRA adapters, vulnerable open-source models from HuggingFace, supply-chain attack via embedding model.
Data & Model Poisoning
Training-data poisoning persists across retraining cycles. Backdoor injection in fine-tuning data. Adversarial examples that bypass safety filters.
Improper Output Handling
LLM-generated content (HTML, SQL, shell commands, code) used downstream without validation, leading to XSS, SQL injection, command injection, deserialization attacks.
Excessive Agency
Agentic systems with overly-broad tool permissions. LLM coerced via prompt injection into destructive actions (sending emails, transferring funds, deleting data).
System Prompt Leakage
Extraction of the system prompt revealing business logic, security instructions, or proprietary IP. Direct extraction via prompt manipulation or side-channel inference.
Vector & Embedding Weaknesses
RAG retrieval poisoning, embedding-collision attacks, vector store enumeration, cross-tenant retrieval leakage in shared embedding databases.
Misinformation
Reliance on hallucinated content for production decisions. Lack of human-in-the-loop on high-stakes outputs. False citation generation.
Unbounded Consumption
Cost-amplification attacks: prompt amplification, recursive agent loops, expensive context-window abuse, denial-of-wallet for LLM-powered SaaS.
METHODOLOGY
AI / LLM Penetration Testing: From Architecture Review to Exploit
AI security testing requires both classical pen-test rigour and AI-specific expertise. We deliver both.
Architecture & Threat Model
LLM stack review, RAG pipeline analysis, agent capability inventory, system prompt review (where authorised), tool permission boundary mapping.
OWASP LLM Top 10 Coverage
Manual probe attacks against each of LLM01-LLM10. Prompt injection chains, jailbreak attempts, RAG poisoning, system-prompt extraction.
Agentic System Exploitation
For agent systems: tool-permission abuse chains. LLM coerced via prompt injection into unauthorised actions (file write, network call, financial transaction).
Report & Retest
OWASP-mapped findings, CVSS scoring, business-impact analysis, free retest within 30 days. Direct engineer access via portal.
CREDENTIALS
Verified Accreditations Auditors Accept
Every credential below is independently verifiable. UK procurement teams, FCA supervisors, ISO 27001 / SOC 2 auditors, and cyber insurance underwriters all recognise these standards.
GET YOUR QUOTE
Get a fixed AI pen test quote in 24 hours
A fixed-price quote back in one business day, from a named CREST assessor. No sales pipeline, no chasing.
- CREST and IASME accredited. Testing your auditors and clients already recognise.
- Fast-track testing within 24 hours where required. Free retest of every fix included.
- Live findings via your client portal, not a four-week PDF.
- Fixed price from £3,500 for a single-role, single-app scope, agreed up front. Most engagements run £5,000 and up. No day-rate surprises.
Dan WilcocksonCo-Founder, CelloriUnder NDA Further named references available on a scoping call.
- We reply within one business day with a fixed-price quote from a named CREST assessor.
- You approve the scope and we book a start date, usually within 24 hours.
- Live findings land in your client portal as we test, with a free retest of every fix.
Get your fixed pen test quote in 24 hours
Quote request received
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COMPLIANCE READY
AI Security Reports Mapped to Every Framework
Findings tagged to OWASP LLM IDs and the AI-specific compliance frameworks UK regulators are establishing.
OWASP LLM Top 10 (2025)
Full coverage of LLM01-LLM10. Each finding pre-mapped to the specific OWASP LLM ID for audit submission.
NCSC AI Code of Practice
UK government’s AI Cyber Security Code of Practice: secure by design, ongoing security, supply chain, transparent reporting.
EU AI Act
High-risk AI system security obligations: Article 15 (cyber security), Article 16 (provider obligations), conformity assessment evidence.
ISO 42001 + ISO 27001
ISO/IEC 42001 (AI management system) plus ISO 27001 A.5.30 (ICT readiness): combined evidence for AI-driven products.
FCA / PRA AI Risk
UK financial regulator AI risk frameworks (FCA AI Discussion Paper, PRA SS1/23 third-party risk): AI testing evidence for regulated firms.
NIS2 + DORA
AI-driven essential services / financial entities: AI testing supports operational resilience evidence under NIS2 and DORA.
PRICING
Transparent AI / LLM Penetration Testing Pricing
All tiers cover the OWASP LLM Top 10. Price varies by AI system complexity: agent capabilities, RAG breadth, fine-tuning scope.
Depends on AI system complexity
Single LLM-powered chatbot, basic RAG (≤100 documents), no agent tools. Typically 5-7 day engagement.
Get a fixed quoteDepends on AI system complexity
Multi-tool agent system, complex RAG pipeline, fine-tuned model, multi-tenant. Typically 8-12 day engagement.
Get a fixed quoteDepends on AI system complexity
Production AI platform, multi-agent orchestration, regulated AI use case (FCA, NHS), custom-trained models. Typically 12-18 day engagement.
Get a fixed quoteBY SECTOR
AI Penetration Testing for Your Sector
Sector-specialist scoping for UK businesses with sector-specific compliance regimes and threat models.
Fintech & FCA-Regulated
FCA-regulated firms, Open Banking, payment APIs, PCI scoping.
Fintech sector pageSaaS Companies
Multi-tenant isolation, SSO/SAML/OIDC, customer-data perimeter, SOC 2 evidence.
SaaS sector pageLaw Firms
Privileged-data confidentiality, partner-tier scrutiny, SRA Cyber Standard alignment.
Law firm sector pageHealthcare
NHS DSPT, NHS DTAC, EHR integration, telehealth, patient-data PII.
Healthcare sector pageInsurance
FCA / PRA Operational Resilience, claims data, broker integrations, cyber underwriting evidence.
Insurance sector pagePublic Sector
CCS / G-Cloud framework, NCSC-aligned, SC-cleared testers available.
Public sector pageWHY EJN LABS
What You Actually Get
Six concrete differentiators that distinguish our AI security service from automated scans and box-tick competitors.
End-to-End OWASP LLM Coverage
OWASP LLM Top 10 manual exploitation, agentic system tool-permission abuse, prompt injection chains, free retests, and AI-aligned compliance evidence.
OWASP LLM Top 10 Aligned
Pre-mapped to LLM01-LLM10 (2025 edition). Findings submitted directly to your AI risk register and audit teams.
NCSC AI Code Aligned
Aligned to the NCSC AI Cyber Security Code of Practice: UK government’s emerging AI security standard.
Practical AI Security Experience
Our team has hands-on experience exploiting production LLM applications, RAG pipelines, and agentic systems, not just academic AI security theory.
UK CREST + IASME + ISO 27001 + ISO 9001
Independently accredited. Verifiable on the CREST marketplace. AI testing reports accepted by FCA, NCSC, and emerging UK AI regulators.
Free Retests Until Validated
Re-test every fixed finding at no extra cost until it is confirmed closed. No time limit, no per-retest fee.
FAQ
Frequently Asked
What is AI / LLM penetration testing?
AI penetration testing is the manual security assessment of AI-powered applications: chatbots, RAG systems, agentic platforms, fine-tuned models. Aligned to the OWASP Top 10 for LLM Applications and the NCSC AI Cyber Security Code of Practice. Tests prompt injection, jailbreak, training-data poisoning, model theft, RAG poisoning, and excessive agency in agent systems.
How is AI testing different from regular pen testing?
Regular pen testing covers OWASP Top 10 (web), MASVS (mobile), API Top 10, infrastructure CVEs. AI testing covers OWASP LLM Top 10: prompt injection, jailbreak, RAG manipulation, training-data poisoning, model theft, agent tool abuse. Different attack surface, different exploitation techniques. Both should be tested for AI-powered applications.
How long does AI penetration testing take?
Single chatbot or RAG system: 5-7 working days. Agent system or fine-tuned model: 8-12 days. Enterprise AI platform with regulated use case: 12-18 days. Test duration is determined during scoping based on system complexity, agent capabilities, and RAG breadth.
How much does AI penetration testing cost in the UK?
Chatbot / basic RAG: £6,000-£12,000. Agent system / complex RAG: £12,000-£25,000. Enterprise AI platform: £25,000+. All quotes are fixed-price after scoping. UK day rates for CREST + AI specialist testers are £1,100-£1,400 per day.
Do you test against the OWASP LLM Top 10?
Yes. Every AI engagement covers all 10 categories of the OWASP Top 10 for LLM Applications (2025 edition). Findings tagged to specific OWASP LLM IDs (LLM01:2025 Prompt Injection, LLM02:2025 Sensitive Information Disclosure, etc.) for audit submission.
Do you test prompt injection attacks?
Yes. Prompt injection (LLM01:2025) is the #1 attack against production LLM applications. We test direct prompt injection (user input attempting to override the system prompt), indirect prompt injection (malicious content in RAG documents or web pages the agent processes), and stored prompt injection (malicious content persisted in vector stores).
Can you test agentic AI systems?
Yes. Agentic system testing is a major focus. We test tool-permission abuse chains, where prompt injection coerces the LLM agent into using its authorised tools (email send, file write, database query, financial transaction) for unauthorised purposes. This is OWASP LLM06:2025 (Excessive Agency).
Do you test RAG systems and vector databases?
Yes. RAG testing covers OWASP LLM08:2025 (Vector & Embedding Weaknesses): retrieval poisoning attacks, embedding-collision attacks, cross-tenant retrieval leakage in shared vector databases (Pinecone, Weaviate, Qdrant, pgvector), and confidential-data exfiltration via clever query construction.
Do you test against the NCSC AI Code of Practice?
Yes. The UK government’s AI Cyber Security Code of Practice provides emerging baseline AI security obligations. Our testing is aligned to its principles: secure by design, secure development, secure deployment, secure operation, ongoing security, security reviews.
Can you test fine-tuned models for backdoors?
Yes. Backdoor detection in fine-tuned models is an advanced AI testing capability. We test for trigger phrases, adversarial examples that bypass safety filters, and supply-chain compromise through tainted fine-tuning datasets or malicious LoRA adapters.
Are your testers UK-based and what AI experience do they have?
All AI testers are vetted UK or international engineers with hands-on AI security experience. Relevant background: practical LLM application development, OWASP LLM Top 10 contributor experience, AI red teaming community participation, plus traditional pen-test certifications (CREST CRT, OSCP).
Do you sign NDAs?
Yes. Standard NDA before any technical detail is shared. AI engagements often involve highly proprietary system prompts, training data, and model weights; we operate under custom MSAs that include AI-specific data handling and IP clauses.
20+ CREST-certified testing services in one place
Web, mobile, API, cloud, AI, infrastructure, red team. Pick the test that fits your environment.
Get a fixed AI pen test quote in 24 hours
A CREST-certified AI specialist tester will contact you within one business day with a fixed price, a realistic timeline, and the named consultant. No sales pipeline.
