AI Browser Extensions: Productivity Tools or Data Thieves?

Many popular AI browser extensions promise to help you draft emails, summarize content, or manage tasks. But a recent investigation by Palo Alto Networks' Unit 42 reveals a darker side: some of these tools are actually malicious, secretly reading your emails, stealing passwords, and exfiltrating sensitive data. They disguise themselves as harmless productivity aids while intercepting your prompts and transmitting them to attackers. This Q&A breaks down the risks, how these extensions operate, and what you can do to protect yourself. For details on the specific data they target, see question 2.

1. How do malicious AI browser extensions disguise themselves?

These extensions often masquerade as legitimate productivity tools—for example, AI assistants that auto-complete emails, generate responses, or summarize web pages. They present clean interfaces, offer free trials, and may even have positive user reviews (sometimes fake). Their true nature is hidden: once installed, they request broad permissions like “read and change all your data on websites you visit.” Users rarely scrutinize these requests. The extensions then quietly activate keyloggers, cookie stealers, or prompt interceptors. They blend in because many AI tools do need extensive permissions, so suspicious activity goes unnoticed. Unit 42 found several such extensions on official stores, downloaded by thousands, before they were flagged.

2. What data do these extensions typically steal?

Malicious AI browser extensions target a wide range of sensitive information. Their primary goal is to harvest everything a user types or views. This includes passwords entered into login forms, credit card numbers, personal messages, and email content (especially since they promise to “help you write”). They also intercept prompts you feed to AI models—this gives attackers insight into your business communications, drafts, and even proprietary data. Beyond keystrokes, they can extract cookies to hijack active sessions, scrape personal details from social media, and download files from cloud services. Unit 42’s analysis showed that some extensions even exfiltrate saved credentials directly from browser password managers. The data is sent to remote servers controlled by cybercriminals, who then use it for identity theft, phishing, or selling on dark web markets.

3. How do they intercept and exfiltrate sensitive information?

The technical mechanism is surprisingly simple. Once installed, the extension injects JavaScript into every page you visit. It listens for events like form submissions, keystrokes, and DOM changes. For email writing, it can capture the entire compose window before it reaches the AI service. The captured data is then encoded (often base64) and sent via HTTP requests to a command-and-control server. Some extensions use WebSocket connections for real-time streaming. To avoid detection, they may delay exfiltration, encrypt traffic, or mimic legitimate API calls. Unit 42 observed cases where the extension pretended to send data to the AI provider but actually routed it elsewhere. They also use obfuscation techniques to hide malicious code from browser extension reviewers. For more on what data is stolen, refer back to question 2.

4. Are popular AI email assistants like Grammarly or Jasper safe?

Not all AI extensions are malicious. Well-known tools like Grammarly, Jasper, or Microsoft Editor have undergone extensive security audits and are generally considered safe—provided you download them from official stores and keep them updated. However, the risk comes from copycat or lesser-known extensions that mimic these brands. Unit 42 warns that even a single malicious extension on your browser can compromise all your online accounts. To stay safe, always research the developer, check permissions carefully, and limit installations to only what you truly need. For a more detailed guide on protective measures, skip to question 5.

5. What should users do to protect themselves from such threats?

To avoid falling victim, follow these cybersecurity best practices:

• Review permissions before installing any extension. If an AI writing tool asks for access to “all websites” or “read and change your data,” question why.
• Stick to official browser stores (Chrome Web Store, Firefox Add-ons) and check ratings, download numbers, and developer reputation.
• Regularly audit your extensions—remove any you don’t recognize or rarely use.
• Use a password manager that doesn’t rely on browser storage, and enable two-factor authentication on critical accounts.
• Keep your browser and security software updated.

If you suspect a malicious extension, immediately uninstall it, run a full antivirus scan, and change your passwords. For more on specific threats, see question 6.

6. What did Unit 42’s investigation specifically uncover?

Unit 42, Palo Alto Networks’ threat intelligence team, analyzed several AI browser extensions that promised to help with email writing and productivity. They found that these extensions were not just reading your emails—they were actively exfiltrating them alongside passwords and prompts. The investigation revealed that attackers used these tools as a vector for credential theft and corporate espionage. Over a six-month period, multiple malicious extensions were identified, some with tens of thousands of installations before removal. The team also observed that the stolen data was being sent to servers in various countries, highlighting the global nature of the threat. This discovery underscores the need for heightened vigilance when granting browser permissions to AI-powered extensions.