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Shut down prompt injection attacks targeting AI email agents and tools

Adversaries use prompt injection attacks to turn your AI against you with agent manipulation, data exfiltration, verdict confusion, and more.

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Prompt injection in a nutshell

Prompt injection attacks attempt to manipulate or deceive the AI agents and tools that have become ubiquitous in email for productivity and security.

Direct prompt injection targets LLM-connected workflows or agent-backed mailboxes to get them to take an unrequested action: exfiltrate data, forward or delete mail, surface a phishing lure, and more.

Indirect prompt injection attacks use hidden text engineered to fool AI/ML email analysis into flipping a malicious verdict toward benign.

Prompt injection
The explosion and sophistication of AI-generated email attacks requires a solution that provides best-in-class efficacy, but also the ability to contextualize and respond to threats in real time. With Sublime, our team can prevent, detect, and respond to email-borne threats of today and the future.
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Brad Jones
CISO, Snowflake

What makes prompt injection so effective

Prompt injection doesn’t target users, so traditional detections and behavioral signals can’t be used to catch these attacks.

Hidden

Hidden

Adversaries try to evade human analysts and security scanner by hiding prompt injection attacks in invisible text and code comments.

Manipulative

Manipulative

Prompt injection uses AI to do its dirty work, turning trusted tools with permissive access into malicious actors.

Invasive

Invasive

AI is integrated into every aspect of digital life. Each new AI agent or tool is a possible attack surface.

Prompt injection attacks are evolving

Prompt injection targeting agents and LLMs through email are a fairly new attack type. This means that they are still in a phase of rapid evolution. You need security that can keep up and stop them no matter what form they take.

Layered detection methods

Sublime uses a combination of AI agents, machine learning, and behavioral analysis to shut down email attacks with industry-leading efficacy.

Built on real-world attacks

Threats evolve daily and Sublime stays current as attacker behavior changes, all while keeping detections grounded in logic you can inspect and adjust.

Autonomous triage and coverage

Our AI-powered Autonomous Security Analyst (ASA) fully automates triage and remediation of user-reported emails. Then our Autonomous Detection Engineer (ADÉ) takes ASA results and closes coverage gaps for novel attacks.

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Latest on prompt injection

The latest news, research, attack spotlights, and product updates.

Attack spotlight

Invoice fraud campaign adds prompt injection aimed at email AI agents

October 26, 2026
Sublime news

Stop email prompt injection to safely enable AI agents in the inbox

October 21, 2026
Attack spotlight

Hiding attacks in plain sight with invisible Unicode tag characters

October 14, 2026

Frequently asked questions

What is prompt injection?

Prompt injection is an attack where malicious instructions are embedded in content that an AI model processes to trick it into following the attacker's instructions instead of the legitimate user's or system's. It's roughly analogous to SQL injection, but targeting AI models instead of databases.

What's the difference between direct and indirect email prompt injection?

Direct injection is when the attacker attempts to manipulate an AI agent or tool into taking a specific action. Indirect injection is when the malicious instructions intend to confuse an AI or traditional ML security system into making an incorrect verdict about an email.

How does prompt injection relate to the email security?

An attacker could send a phishing email containing injected instructions targeting an AI email assistant. If the assistant processes the email and acts on it (summarizing, replying, filing), the injected instructions could redirect its behavior to exfiltrate other emails, send replies on the user's behalf, or manipulate its outputs.

Can prompt injection be fully prevented?

Not currently. There's no complete technical solution. Mitigations include input sanitization, privilege separation, keeping sensitive actions behind human confirmation steps, and limiting what data the model can access. It's treated more like a risk to manage than a problem to fully solve.

What is a prompt injection attack against a RAG system?

Retrieval-Augmented Generation systems pull external documents into the model's context to answer questions. An attacker who can influence what documents get retrieved — by poisoning a knowledge base, a shared drive, or a webpage — can inject instructions that appear to the model as legitimate context, hijacking its responses or actions.

Now is the time

See how Sublime delivers autonomous protection by default, with control on demand.