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Introduction
As of March 2026, over 115 million users rely on AI‑powered browser extensions for platforms such as ChatGPT, Claude, Microsoft Copilot, Google Gemini, and DeepSeek【1†L1-L2】. However, threat actors are exploiting this massive ecosystem by distributing malicious extensions disguised as legitimate productivity tools, turning them into data stealers that compromise credentials and sensitive information. This article dissects the technical indicators of these attacks, provides hands‑on commands to detect and remove dangerous extensions, and outlines actionable security controls for both individual users and corporate environments.
Learning Objectives
– Identify malicious browser extensions targeting generative AI accounts by analyzing permissions, network traffic, and code artifacts.
– Apply Linux, Windows, and browser‑specific commands to detect, block, and remove data‑stealing add‑ons.
– Implement extension management policies and API security measures to safeguard credentials across ChatGPT, Claude, Copilot, Gemini, and DeepSeek.
You Should Know
1. How Malicious AI Extensions Operate – A Technical Deep Dive
Attackers publish seemingly useful add‑ons – such as “ChatGPT History Exporter” or “Gemini Quick Reply” – on official Chrome Web Store or third‑party marketplaces. Once installed, these extensions request broad permissions: `storage`, `cookies`, `webRequest`, `tabs`, and `
– Read and exfiltrate all cookies from `chat.openai.com`, `claude.ai`, `copilot.microsoft.com`, `gemini.google.com`, and `deepseek.com`.
– Intercept and modify API requests, injecting extra headers to steal session tokens.
– Periodically send stolen data to remote C2 servers via background scripts (service workers).
A concrete example: In early 2026, researchers discovered an extension called “AI Assistant Pro” that, after installation, added a hidden script to extract `session_token` from ChatGPT’s local storage and POST it to `https://evil-stealer[.]com/log`. The same script targeted Claude’s `sessionKey` and Gemini’s `access_token`.
Detection – Linux / macOS (Chromium‑based browsers)
List all extensions with their IDs and version ls ~/.config/google-chrome/Default/Extensions/ Inspect manifest.json of a suspicious extension (replace EXTENSION_ID) cat ~/.config/google-chrome/Default/Extensions/EXTENSION_ID//manifest.json | jq '.permissions' Check for suspicious network calls in extension background scripts grep -r "fetch\|XMLHttpRequest\|chrome.storage" ~/.config/google-chrome/Default/Extensions/EXTENSION_ID/
Detection – Windows (Chrome/Edge)
:: List Chrome extensions
dir "%LOCALAPPDATA%\Google\Chrome\User Data\Default\Extensions"
:: Check Edge extensions
dir "%LOCALAPPDATA%\Microsoft\Edge\User Data\Default\Extensions"
:: Use PowerShell to examine extension permissions
Get-ChildItem -Path "$env:LOCALAPPDATA\Google\Chrome\User Data\Default\Extensions" -Recurse -Filter "manifest.json" | ForEach-Object { Get-Content $_.FullName | Select-String "permissions" }
Step‑by‑Step Guide to Remove a Malicious Extension
1. Open Chrome/Edge and navigate to `chrome://extensions` (or `edge://extensions`).
2. Enable “Developer mode” (toggle in top right).
3. Click “Details” on any extension you suspect.
4. Check the “Permissions” section – revoke access to “All sites” if not strictly required.
5. Copy the extension ID (long string in the URL).
6. Uninstall immediately, then verify removal: the extension folder should be gone from the above paths.
7. As a precaution, clear all cookies and site data for the targeted AI domains (Settings → Privacy and Security → Clear browsing data).
2. Advanced Threat Hunting – Monitoring Extension Traffic and API Abuse
Even after removal, compromised session tokens may still be active. Attackers often sell stolen tokens on underground forums, leading to account takeover (ATO). To detect ongoing abuse, you must monitor outbound traffic and audit API activity logs.
Linux – Capture all traffic from Chrome to check for beaconing
Use tcpdump to capture HTTP/HTTPS traffic from Chrome process (replace PID) sudo tcpdump -i any -s 0 -A 'tcp port 80 or tcp port 443' | grep -E "POST|GET|evil-domain" Alternatively, use mitmproxy to intercept and inspect all browser traffic mitmproxy --mode regular --showhost Then configure Chrome to use proxy 127.0.0.1:8080
Windows – Monitor extension network activity with PowerShell
Get established connections from browser processes
Get-1etTCPConnection | Where-Object { $_.OwningProcess -in (Get-Process chrome,msedge).Id } | Format-Table LocalAddress, LocalPort, RemoteAddress, RemotePort, State
Use Sysmon (if installed) to log network connections
Get-WinEvent -FilterHashtable @{LogName='Microsoft-Windows-Sysmon/Operational'; ID=3} | Where-Object { $_.Message -match "chrome.exe|msedge.exe" }
API Security Hardening – Rotate and Revoke Tokens
If you suspect a token leak for any AI platform, immediately rotate the API key or session token. For enterprise users with programmatic access:
– ChatGPT API: Revoke old keys at `https://platform.openai.com/api-keys`.
– Claude API: Regenerate keys at `https://console.anthropic.com/settings/keys`.
– Gemini API: Delete compromised keys at `https://aistudio.google.com/app/apikey`.
– Copilot / Bing: Sign out of all devices (Microsoft account security dashboard).
– DeepSeek: Contact support or use the “Sign out all devices” feature if available.
Step‑by‑Step Guide to Lock Down Your AI Accounts
1. Enable MFA (Multi‑Factor Authentication) on every AI platform that supports it.
2. Generate new API keys and delete the old ones.
3. Use a dedicated password manager with browser extension isolation (e.g., Bitwarden, 1Password) – never allow AI extensions to access stored passwords.
4. Configure Chrome’s “Extension security” policy: go to `chrome://policy` and enforce “ExtensionSettings” to block all extensions except those from an allowlist.
3. Hardening the Browser Against Extension‑Based Data Stealers
Prevention is far more effective than detection. Both individuals and organizations can enforce strict controls to block malicious add‑ons before they ever run.
For Individual Users (Chrome/Edge)
– Disable “Allow access to file URLs” for all extensions (under extension details).
– Review extension permissions quarterly – revoke any extension that requests `cookies`, `webRequest`, or `tabs` without a clear need.
– Install only from verified publishers and avoid “Please read before install” pages that hide permission warnings.
For Enterprise – Group Policy (Windows)
:: Block all extensions and allow only specific IDs via Group Policy :: Chrome: Computer Configuration -> Administrative Templates -> Google Chrome -> Extensions :: Configure "Configure extension installation blocklist" = :: Configure "Configure extension installation allowlist" = ALLOWED_EXTENSION_ID_1;ALLOWED_EXTENSION_ID_2
For Enterprise – Linux (Chrome policies)
Create policy file /etc/opt/chrome/policies/managed/extension_policy.json
sudo mkdir -p /etc/opt/chrome/policies/managed
sudo tee /etc/opt/chrome/policies/managed/extension_policy.json <<EOF
{
"ExtensionInstallBlocklist": [""],
"ExtensionInstallAllowlist": ["ghbmnnjooekpmoecnnnilnnbdlolhkhi", "nmmhkkegccagdldgiimedpiccmgmieda"],
"ExtensionSettings": {
"": {
"installation_mode": "blocked"
}
}
}
EOF
Step‑by‑Step Guide to Audit Existing Extensions
1. Export a list of all installed extensions with their permissions using a tool like `chrome‑extension‑audit` (Node.js):
npm install -g chrome-extension-audit chrome-extension-audit --browser chrome --output csv > extensions.csv
2. Manually review each entry, looking for permissions like `cookies`, `webRequest`, `webRequestBlocking`, `proxy`, or `clipboardRead`.
3. Search the extension ID on [CRXcavator](https://crxcavator.io/) to see risk scores and code analysis.
4. For any extension rated “High” or “Critical”, immediately uninstall and report it to the Chrome Web Store using the “Report abuse” link.
4. What to Do If You’ve Already Been Compromised – Incident Response Playbook
If you find evidence that a malicious extension has already stolen your AI account credentials or API keys, follow this IR plan:
Step 1 – Containment
– Immediately disconnect the affected machine from the internet (disable Wi‑Fi / unplug Ethernet).
– Remove the malicious extension using the steps in Section 1.
– Revoke all session tokens and API keys for every AI platform.
Step 2 – Eradication
– Run a full antivirus scan (Windows Defender, Malwarebytes, or ClamAV on Linux).
– On Windows, use `Sysinternals Autoruns` to check for persistence mechanisms that the extension might have dropped.
– On Linux, inspect crontab and systemd timers for unexpected entries:
crontab -l sudo systemctl list-timers
Step 3 – Recovery
– Change passwords for all associated email accounts (since AI accounts often use email for password reset).
– Enable account recovery notifications (SMS or authenticator app).
– Restore the browser profile from a clean backup (if available).
Step 4 – Post‑Incident Monitoring
– Set up a free alert using [Have I Been Pwned](https://haveibeenpwned.com) for your email address.
– For corporate environments, implement a browser extension allowlist policy (as described above) to prevent recurrence.
What Undercode Say
– Key Takeaway 1: Browser extensions represent a critical, often overlooked attack vector for AI platforms. The same convenience that makes extensions appealing – deep access to web content and cookies – is precisely what attackers weaponize.
– Key Takeaway 2: Defending against these threats requires a layered approach: technical controls (permission audits, network monitoring, group policies) combined with user education (avoiding over‑permissioned extensions and enabling MFA on every AI account).
Analysis: The rapid adoption of agentic AI has outpaced security awareness among both individual users and enterprises. While AI providers invest heavily in backend security, client‑side threats like malicious browser extensions remain largely unaddressed. Traditional endpoint protection often misses extension‑based stealers because they operate within the browser’s trusted context. Therefore, organizations must adopt browser‑specific security tools (e.g., Chrome Enterprise policies, Microsoft Defender for Endpoint’s browser extension control) and regularly audit all third‑party add‑ons. Additionally, AI platforms should implement anomaly detection for session token reuse from unexpected IP addresses and offer one‑click “revoke all sessions” features. Without these measures, the 115 million users of AI extensions will continue to be at risk.
Prediction
– +1 By 2027, major browser vendors will integrate AI‑specific permission models (e.g., separate consent for “accessing ChatGPT” vs. “modifying network requests”), significantly reducing the attack surface.
– -1 Until then, the number of reported extension‑based account takeovers for AI services will increase by at least 40% year‑over‑year, as attackers continue to profit from stolen API keys and session tokens sold on darknet markets.
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