LLM09 · OWASP LLM Top 10

Misinformation (LLM09)

An LLM generates incorrect or misleading content that the user trusts and acts on. Hallucination is the obvious case; sycophancy and manipulated outputs are subtler. Misinformation becomes a security risk when it leads to operational decisions, legal advice, or downstream automation that depends on accuracy.

Rank
LLM09 of 10
In the check
Not cited directly by a question
LLM01
Prompt Injection
LLM02
Sensitive Information Disclosure
LLM03
Supply Chain
LLM04
Data and Model Poisoning
LLM05
Improper Output Handling
LLM06
Excessive Agency
LLM07
System Prompt Leakage
LLM08
Vector and Embedding Weaknesses
LLM09
Misinformation
LLM10
Unbounded Consumption
Figure 1. The OWASP LLM Top 10, with LLM09 marked.
In practice

What it looks like in practice

Three shapes this risk takes in real deployments.

Example 1

An LLM-based legal-research tool cites cases that do not exist.

Example 2

A chatbot's hallucinated security advice causes a customer to misconfigure access controls.

Example 3

A coding assistant suggests a non-existent npm package, which an attacker then registers maliciously.

Controls

Controls that close it

The controls the check looks for when this entry applies.

Output validation against source-of-truth where possible

User-facing confidence indicators

Disclaimer and human-review workflows for high-stakes outputs

Hallucination testing as part of release

Posture Check

Where the check cites it

The AI Posture Check cites OWASP LLM Top 10, including this entry, when placing you at Crawl, Walk, Run or Sprint.

The questions cite the control frameworks a regulator would expect you to hold: NIST AI RMF, ISO 42001 and the OWASP LLM Top 10. Your stage on the check is a starting point for an EU AI Act conformity review, not a substitute for one.

Ready when you are

Score yourself against this framework.

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