The New Frontier of Browser Exploits
For years, browser extensions have represented a double-edged sword for digital security. While they offer unprecedented customization, productivity boosts, and ad-blocking capabilities, they also operate with expansive privileges inside the user's web client. Now, as tech giants race to embed generative artificial intelligence directly into the browsing experience, cybersecurity researchers have uncovered a troubling reality: the architecture designed to connect browser extensions with underlying web environments can be weaponized to hijack integrated AI assistants.
Security firm Forever Security recently demonstrated that a single, deceptively simple browser extension can quietly seize control of the built-in AI tools across multiple modern browsers. The vulnerability affects a broad spectrum of products built on or around Chromium architectures, including Google Chrome’s Gemini features, Perplexity Comet, Microsoft Edge’s Copilot integration, Opera Neon, and Anthropic's Claude Chrome extension.
This discovery highlights a critical oversight in the rapid deployment of browser-native artificial intelligence. Rather than requiring complex zero-day exploits or elevated operating system privileges, attackers can leverage standard, benign-looking extension permissions to manipulate the AI context, extract confidential prompt histories, and trigger autonomous actions on behalf of the user.
Understanding the Attack Vector
To understand how a single extension can compromise widely varying AI tools, one must examine how modern browsers expose these intelligence models to the DOM (Document Object Model) and internal APIs. When browser vendors integrate an assistant, they frequently expose helper interfaces that allow the AI to read web page contents, summarize text, assist with form completion, or execute search commands.
When a user installs a malicious or compromised extension, it typically requests access to read and modify site data. In a traditional threat model, this access allows the extension to inject scripts, read cookies, or log keystrokes on specific websites. However, in an AI-integrated ecosystem, the boundary between page content and browser functionality becomes dangerously blurred.
The research reveals that once installed, the attacker's extension can communicate with the background scripts and exposed endpoints used by embedded assistants. By making structured calls to these endpoints, the rogue extension can interact with the host browser’s assistant automatically. The user does not even need to open the assistant’s interface; a single click or background event triggered by the extension is sufficient to execute commands, feed malicious prompts to the model, or siphon data sent to and from the AI inference engine.
Cross-Platform Vulnerability: Chrome, Edge, Comet, and Beyond
What makes this vulnerability particularly alarming is its cross-product footprint. The underlying mechanism does not rely on a flaw unique to a single company's code base, but rather on shared conceptual patterns in how Chromium handles extension contexts alongside high-privilege AI integrations.
Google Chrome and Gemini Live
In Chrome, Google has increasingly bound its Gemini capabilities into the address bar, side panels, and contextual menus. An extension running in this environment can leverage existing DOM permissions to monitor when Gemini interacts with page content. By injecting subtle text into web pages or directly invoking background message passes, the extension can trick Gemini into processing adversarial instructions without user awareness.
Microsoft Edge and Copilot
Microsoft Edge has pioneered the heavy integration of Copilot directly into the sidebar. Because Edge’s architecture grants the assistant deep visibility into the open tab to perform actions like page summarization or document translation, an extension capable of manipulating the active page's context can perform prompt injection attacks. Furthermore, the researchers found that extension scripts could invoke the local web sockets or IPC mechanisms used by Edge to pass data to Copilot.
Perplexity Comet and Specialized AI Browsers
Emerging browsers like Perplexity Comet place AI directly at the center of the user workflow. Because the entire user experience revolves around persistent assistant interaction, the interface boundaries are even thinner. An extension operating in Comet can intercept search queries, alter the output before it renders to the screen, or query the embedded assistant for saved session information, effectively turning the AI into a surveillance instrument.
Claude via Extension Contexts
Anthropic’s Claude extension for Chrome operates as a bridge between the browser window and Claude’s cloud platform. The researchers demonstrated that third-party extensions sharing the browser context can exploit communication channels between extensions—a process known as cross-extension messaging—to send unauthorized prompts to Claude, exfiltrating the responses back to an attacker-controlled server.
The Threat of Indirect Prompt Injection
Beyond direct command execution, the ability for an extension to manipulate the browser’s AI assistant opens the door to devastating indirect prompt injection scenarios.
Consider a user researching financial documents or reviewing sensitive personal emails within their browser. If an extension silently inserts hidden system prompts into the web pages being viewed, and the integrated assistant reads those pages, the AI model can be hijacked dynamically. The AI might be instructed to summarize the document while simultaneously appending confidential personal data to an outgoing web request disguised as a innocent tracking pixel.
Because users tend to trust responses from native browser assistants, they are unlikely to suspect that the answers provided by their sidebar interface have been manipulated or that their input prompts are being monitored and altered in real time.
Why Traditional Extension Permissions Fail
This security breakdown highlights a structural flaw in current browser security models. Manifest V3, Google’s updated browser extension framework, was explicitly designed to enhance privacy and security by limiting the execution of remotely hosted code and restricting permissions.
However, Manifest V3 was conceived before generative AI was deeply baked into browser platforms. Manifest V3 controls which web requests an extension can make and which scripts it can inject into a page, but it does not account for the semantic interface created by an embedded language model. If an extension has permission to read a web page, and the browser’s native AI also reads that web page to assist the user, the boundary between normal browsing and unauthorized command execution disappears.
Current extension permission prompts fail to convey this risk to end users. A user who approves an extension request to "read and change all your data on the websites you visit" expects the extension to interact with web pages, not to gain an implicit backdoor into the browser's conversational AI models or corporate search history.
Mitigation Strategies and Open Questions
Addressing this vulnerability requires browser vendors and AI developers to re-evaluate how contextual tools interact with third-party software. Simply patching individual endpoints will not be enough; fundamental design changes are required.
- Context Isolation: AI assistants must treat all DOM content and external extension messages as untrusted untranslated input. Strict boundaries must prevent models from executing actions based on prompt instructions found inside web pages or cross-extension communication channels.
- Explicit Explicit Authorization: High-privilege AI operations—such as summarizing personal email, accessing local browser history, or executing code—should require explicit, out-of-band user approval that cannot be bypassed or automated by extensions.
- Updated Permission Frameworks: Extension stores must introduce specific disclosure requirements and security flags for extensions that interact with browser-level AI APIs or read pages where assistants operate.
As AI shifts from isolated chat web applications to ambient software built into the fabric of our operating systems and web browsers, the attack surface expands exponentially. The research from Forever Security serves as a stark warning: without rigorous isolation between extension runtimes and AI models, our smartest browsing tools may become our biggest security blind spots.
