Identifying and Securing Unsanctioned Browser Extensions

Article summary: Browser extensions feel small but they operate inside your browser with access to passwords, session tokens, browsing activity and the content of every page your team visits. A quarterly audit process, a clear approval path and permission-based review close most of these gaps without disrupting how your team works.

Browser extensions have a reputation for being small and harmless helpers. A grammar checker. An ad blocker. A tab manager.

That reputation is why they are one of the most effective attack surfaces in modern business IT.

An extension doesn’t live outside your browser. It lives inside it with access to everything you type, everything you view and (in many cases) the credentials you use across every site you visit.

Strong business security increasingly depends on what happens inside the browser rather than just at the network edge. Most organizations have no policy for the extensions sitting in their employees’ browsers right now.

Why Browser Extensions Are a Bigger Risk Than They Look

99% of enterprise employees have browser extensions installed. 53% of those extensions carry high or critical-risk permissions that grant access to cookies, passwords, browsing history or page content.

Those numbers come from LayerX’s 2025 Enterprise Browser Extension Security Report which is the first study to combine public marketplace statistics with real-world enterprise usage data. 

The picture it paints isn’t of a few bad actors. It is of a near-universal risk surface that most organizations have not looked at.

In December 2024, a supply chain attack on the Chrome Web Store exposed more than 3.2 million users to extensions that had silently turned malicious.

A detailed investigation by GitLab’s security team traced the incident to attackers compromising developer accounts through phishing and then pushing malicious updates to previously trusted extensions. The updates harvested session cookies and credentials silently. The extensions had excellent reviews. Users had no reason to be suspicious.

It is a risk pattern similar to phishing-based account compromise. The entry point is social engineering. The payload is silent data exfiltration and exposure can last for days before anyone notices.

Three Categories of Risky Extension

Not every risk looks the same. Understanding the categories helps prioritize the response.

Actively Malicious Extensions

These are extensions built with bad intent or ones that became malicious after a legitimate developer’s account was compromised. 

The December 2024 Chrome Web Store attack is a high-profile example. At least 33 extensions were found to be malicious after attackers hijacked developer accounts via phishing. 

Once updated, the extensions exfiltrated credentials and session cookies from every user’s active browser sessions.

Over-Permissioned Legitimate Extensions

Many extensions that are not malicious still request far more access than their function requires. A tab organizer that asks to read all page content, modify cookies and access browsing history has permissions well beyond what it needs.

These over-permissioned extensions create risk even when the developer’s intentions are benign. The permissions become an attack surface if the developer account is ever compromised.

Abandoned and Outdated Extensions

The LayerX report found that 51% of extensions in enterprise environments haven’t received a developer update in more than a year. An extension that stopped receiving security updates is a vulnerability waiting to be exploited. Attackers actively monitor the extension ecosystem for dormant tools with large user bases and broad permissions as they make ideal targets for account takeover.

A Browser Extension Audit Checklist

Browser extension security doesn’t require specialist tools. It requires a process. 

Our guide to running a shadow IT audit covers a similar methodology for other unsanctioned software and the same principles apply to extensions.

1. Take a full inventory across your team.

Ask every employee to open their browser extension settings and share what they have installed. Many will find extensions they forgot about or can’t explain why they installed. 

In a managed environment, your IT tools should be able to pull this list automatically. In an unmanaged one, a quick self-reported audit is a fast starting point.

2. Review what permissions each extension holds.

For each extension, look at what it can access. 

Pay particular attention to extensions with access to all sites, the ability to read page content or form data, access to cookies or stored credentials or the ability to run scripts. These permissions create meaningful exposure regardless of the developer’s intent.

3. Remove anything inactive, unrecognized or outdated.

If an extension hasn’t been used in the last 30 days or if the employee can’t explain what it does, remove it. If it hasn’t received a developer update in over a year treat it as a liability. 

An inactive extension with broad permissions is a dormant risk that provides no ongoing value.

4. Establish an approval path for new extensions.

Create a simple policy. Before installing any new browser extension on a work device, employees submit a brief request. IT reviews the extension’s permissions and publisher and then approves or declines. 

This doesn’t need to be slow. A lightweight form and a 24-hour turnaround keeps the process usable without leaving the decision entirely to individual judgment.

5. Set a quarterly review cadence.

The extension landscape changes constantly. New versions can change permissions. Developer accounts can be compromised. Extensions that were safe six months ago may not be safe today. A quarterly check takes less than an hour per device. Do it before a problem appears rather than after.

Is Your Browser Environment Part of Your Security Picture?

Browser extension security is one of the easiest gaps to close and one of the most consistently overlooked. The risk is real. The audit process is simple. The cost of not doing it can be significant.

Contact Sound Computers to schedule a consultation. We can help you take stock of what is running in your team’s browsers, build a practical approval process and put a regular review schedule in place. Call us at (860) 577-8060, reach us online or email info@soundcomputers.net.

Article FAQs

Why are browser extensions a security risk?

Browser extensions operate inside the browser with permissions to read page content, access cookies and monitor browsing activity. Even legitimate extensions can become a risk if they request excessive permissions, stop receiving security updates or have their developer accounts compromised and used to push malicious updates automatically.

How do I know if a browser extension is safe?

Check what permissions it requests, when it was last updated and whether the publisher is identifiable and established. An extension that asks for access to all sites, form data and cookies when it is a simple productivity tool is over-permissioned. One that hasn’t been updated in more than a year carries additional risk regardless of its original purpose.

What should I do if an employee has an unsanctioned extension installed?

Remove it and document it. Then use the instance to start a broader audit across the team. Most employees don’t install extensions with bad intent. They install what seems useful. A clear policy and a fast approval process redirects that behavior without creating friction.