In the past two years, businesses have been trying to fit large language models (LLMs) into support, analytics, development, and internal automation like never before.
Along with the increasing adoption of (2025) lists prompt injection as LLM01, identifying it as the most critical category of LLM‑specific vulnerabilities, for the — built on frontline intelligence across more than 280 tracked adversaries — documented that threat actors injected malicious prompts into legitimate generative AI tools at more than 90 organizations in 2025. They then used those injections to generate commands that stole credentials and cryptocurrency. The report stated it plainly: "Prompts are the new malware." AI-enabled adversaries increased their overall attack volume by 89% year-over-year, with prompt injection working as both an entry point and a force multiplier.
Real‑world incidents illustrate the operational impact. In August 2024, disclosed EchoLeak (CVE-2025-32711, CVSS 9.3), the first documented zero-click prompt injection exploit against a production AI system, targeting Microsoft 365 Copilot. By sending a single crafted email, no user interaction required, an attacker could cause Copilot to access internal files and transmit their contents to an attacker-controlled server.
Both vulnerabilities to process instructions, summarize information, and trigger automated workflows, but it is difficult for LLMs to tell:
Instructions from data
Information from context
Context from metadata
User intent from metadata
This creates an opportunity for attackers to manipulate and influence the model's behavior, either directly or indirectly.
Modern prompt injection
Cross-model prompt injection
LLM use is a common practice among enterprises. Attackers corrupt the output of a particular model, knowing well that other models would be processing the content. Hence, the corruption propagates through all AI systems.
RAG supply chain poisoning
Attackers create malicious information — documentation, blog articles, GitHub READMEs. Then they wait until this malicious information is ingested in enterprises' RAG pipelines, then use it as an attack vector.
Agent hijacking
AI agents have evolved to the point where they can send emails, modify cloud infrastructure, execute code snippets, and interact with internal corporate systems. It takes just a single instruction to make agents act differently in a harmful manner.
Context overflow attacks
With the help of million-token context windows, attackers place malicious code within the document and hope that an LLM will stumble upon it and execute it, thus overriding all previous instructions.
Memory poisoning
Due to the implementation of long-term memory in LLMs, attackers can inject instructions that permanently reconfigure their state.
Model‑router manipulation
Enterprises increasingly use model routers to select between multiple LLMs. Attackers craft prompts that force routing to the weakest or least‑guarded model.
Why this matters for business leaders
Prompt injection is not a theoretical problem. It directly affects:
Customer‑facing systems (chatbots, support agents)
Internal copilots (developer tools, security assistants)
Automation workflows (ticketing, cloud operations, HR processes)
Data governance (RAG pipelines, knowledge bases)
The risk is no longer limited to "the model said something it shouldn't."
In 2026, prompt injection can:
Trigger unauthorized actions
Leak sensitive data
Corrupt internal workflows
Manipulate analytics
Alter business logic
Compromise multi‑agent systems
The attack surface has expanded dramatically.
What enterprises should do now
1. Constrain model permissions
Limit what the model can do, not just what it should do.
2. Segment untrusted content
Treat all external data — including RAG sources — as potentially hostile.
3. Monitor tool invocation
Require human approval for high‑impact actions.
4. Validate content provenance
Ensure RAG pipelines don't ingest poisoned external content.
5. Harden model routers
Prevent attackers from forcing routing to weaker models.
6. Treat LLMs as untrusted components
This mindset shift is the foundation of modern AI security.
The bottom line
Prompt injection remains the most effective way to compromise enterprise AI systems because it exploits the fundamental way LLMs interpret text. Until organizations treat LLMs as untrusted interpreters — not autonomous decision‑makers — prompt injection will continue to dominate the AI threat landscape.
Julie Brunias is an AI Security Architect.
SOCIAL SHARE CARD GENERATOR