The “Man-in-the-Prompt” Attack: When Your Browser Extension Becomes Your Worst Security Nightmare
Security researchers reveal a critical vulnerability allowing browser extensions to silently intercept, modify, and steal data from AI conversations in ChatGPT, Gemini, and other platforms, affecting 99% of enterprise users.
Picture this scenario: You’re using ChatGPT to draft a confidential business proposal, completely unaware that a browser extension you installed months ago—perhaps a productivity tool or ad blocker—is silently recording every word you type and every response you receive. This isn’t science fiction. It’s happening right now through what security researchers call the “Man-in-the-Prompt” attack, and it’s affecting every major AI platform you use.
Understanding the Invisible Threat in Your Browser
Let me explain how this works in terms that make sense for your daily workflow. When you interact with AI tools like ChatGPT, Gemini, or Claude through your browser, your prompts become part of the webpage’s structure—what developers call the Document Object Model or DOM. Think of it as the blueprint of everything visible and invisible on your screen.
Here’s where things get concerning: Any browser extension with basic scripting permissions can read and modify this blueprint. According to LayerX Security’s groundbreaking research from July 2024, even extensions without special permissions can hijack your AI conversations. The research confirms that ChatGPT’s 5 billion monthly visits, Gemini’s 400 million, and every other major AI platform are vulnerable to this attack vector.
What makes this particularly insidious? The attack leaves absolutely no trace. As documented by security researchers at Hackread, malicious extensions can inject hidden prompts, steal responses, and then delete the entire conversation history—all while you continue working, blissfully unaware.
The Command and Control Infrastructure: How Hackers Orchestrate the Attack
Here’s what actually happens behind the scenes:
When a compromised extension infiltrates your browser, it doesn’t work alone. It establishes a connection to a remote server controlled by attackers, the command and control (C2) server. Think of it as a puppet master pulling strings from afar. The extension opens WebSocket connections—essentially creating a two-way communication channel that allows real-time command execution.
I’ve seen demonstrations where these extensions can receive instructions to change their behavior on the fly. Need to target a specific company’s data? The C2 server updates the attack parameters. Want to avoid detection during a security audit? The malicious behavior can be temporarily disabled, then reactivated later.
The sophistication here is remarkable. LayerX’s proof-of-concept demonstrations showed extensions opening background tabs invisible to users, injecting prompts into AI systems, extracting responses containing sensitive data, and transmitting everything to remote servers—all while maintaining the appearance of a legitimate browser extension.
Real-World Impact: When Theory Meets Practice
Let’s talk about what this means for your organization. According to the research, 99% of enterprise users have at least one browser extension installed. More than half use over ten extensions. Each one represents a potential entry point for attackers.
Consider this workplace scenario: Your marketing team uses Gemini integrated with Google Workspace. A team member has installed what appears to be a helpful grammar-checking extension. Unknown to them, this extension is compromised. As Dark Reading reports, even with the Gemini sidebar closed, the malicious extension can:
- Extract emails discussing product launches
- Access strategic documents from Google Drive
- Harvest contact lists of key clients
- Steal meeting summaries containing financial projections
The traditional security tools your IT department relies on—Data Loss Prevention systems, Secure Web Gateways, Cloud Access Security Brokers—they’re all blind to these DOM-level manipulations. It’s like having state-of-the-art locks on your doors while leaving the windows wide open.
Why Your Current Security Measures Are Failing
Here’s an uncomfortable truth: The security infrastructure most organizations built over the past decade wasn’t designed for the AI era. As Mayank Kumar from DeepTempo noted in his analysis shared with Hackread, “Prompts are not just text, they are interfaces.”
This paradigm shift means your security team faces several challenges:
Traditional network monitoring watches data flowing in and out of your network but can’t see what’s happening inside the browser itself. It’s like trying to prevent shoplifting by only watching the store’s entrance while ignoring what happens in the aisles.
Even Google’s Manifest V3—their latest attempt to secure Chrome extensions—hasn’t solved the problem. Extensions still only need minimal permissions like “activeTab” and “scripting” to execute these attacks. The permission model that’s supposed to protect you is fundamentally flawed because it doesn’t account for how AI tools process information.
What’s particularly troubling is the supply chain vulnerability. Legitimate extensions can be compromised through developer account takeovers. That productivity extension you’ve been using for years? It could receive a malicious update tomorrow, and you’d never know.
Practical Steps to Protect Your Organization
So what can you actually do about this? Let me give you actionable steps rather than theoretical concepts:
Immediate Actions for Monday Morning:
First, conduct an extension audit. Don’t just list what’s installed—understand why each extension exists and who approved it. I’ve seen organizations discover dozens of extensions they didn’t even know were in use.
Second, implement a whitelist approach. Instead of trying to block bad extensions (a losing game), only allow specific, vetted extensions that your security team has reviewed. Yes, users will complain. But would you rather deal with complaints or data breaches?
Third, treat AI prompts like passwords. You wouldn’t type your password into an untrusted field, so why input sensitive business data into an AI tool without considering the security implications?
Building Long-term Resilience:
Deploy browser security platforms that monitor DOM-level interactions. These newer tools can detect when extensions attempt to access AI prompt fields and alert your security team in real-time.
Establish secure AI usage policies. Create dedicated, extension-free browser profiles for sensitive AI work. It’s like having a clean room for handling confidential materials—no unnecessary contamination risks.
Consider implementing behavioral analysis for extensions. Instead of just checking permissions, monitor what extensions actually do. An extension that claims to block ads shouldn’t be accessing your AI conversations.
The Evolution We’re Witnessing
What we’re seeing isn’t just another security vulnerability—it’s a fundamental shift in how cyberattacks operate. The “Man-in-the-Prompt” phenomenon represents the collision of three powerful forces: the widespread adoption of AI tools, the inherent vulnerabilities in browser architecture, and the sophistication of modern attackers.
As we move through 2025, this attack vector will likely evolve. Attackers are already using AI to generate more convincing malicious extensions, complete with professional descriptions and fake reviews. The same technology that’s revolutionizing productivity is being weaponized against us.
Moving Forward: A New Security Mindset
The reality is stark: If you’re using AI tools through a browser with extensions installed, you’re at risk. Period. This isn’t about fear-mongering—it’s about understanding the actual threat landscape you’re operating in.
Organizations need to fundamentally rethink their approach to browser security. The old model of “install whatever helps you work better” is dead. In its place, we need a zero-trust approach to browser extensions, especially when AI tools are involved.
Remember, these attackers aren’t sitting idle. While security teams scramble to understand AI risks, criminals are already exploiting these vulnerabilities. The question isn’t whether your organization will be targeted—it’s whether you’ll be prepared when it happens.
The “Man-in-the-Prompt” attack isn’t just a technical vulnerability; it’s a wake-up call. As AI becomes central to business operations, securing these tools isn’t optional—it’s essential for survival in the digital economy. The organizations that understand this and act accordingly will thrive. Those that don’t may find their most sensitive data in the hands of competitors or criminals, with no trace of how it got there.