Browser Extensions

 

We rely on browser extensions for convenience, but most people have no idea how much access they grant. This blog post highlights why that kind of blind trust can be dangerous.

Problem:
Browser extensions are extremely powerful because they run inside your active web sessions. When you grant an extension permission to read or change data on the sites you visit, you are giving it access to your digital life. That convenient ad blocker or productivity tool you have installed can do serious damage including reading your passwords. Most extensions people install require broad access to function, especially ad blockers. Extension stores like the Chrome Web Store do scan for spyware, but malicious plugins still slip through. Many of us practice good cyber hygiene with strong passwords, 2FA, and password managers, but when it comes to browser extensions, people often overlook the risk and trust the developer or the store without thinking. The real danger is that extensions operate natively inside the browser, so their actions look completely legitimate to security tools.

Solution:
If you install browser extensions, and most people do, ask yourself whether you truly need them and whether the risk to your online data is worth it. If you cannot live without an ad-blocker extension, which is true for almost all users, consider using DNS‑level ad blocking with something like Pi‑hole instead of a browser extension. DNS‑based blocking works across all devices on your network rather than on each device or browser separately. A much safer approach is to keep a separate browser with zero extensions installed for sensitive tasks like banking or email. I follow this myself in addition to using Pi‑hole for network‑wide ad blocking.

Working demonstration:
To show how dangerous extensions can be, I wrote a working browser extension (link below) that you can install. If you are curious, try it and see the level of access a browser extension actually has.

Extension Telemetry Demo

The screenshot below is from this extension running in my Chrome browser, showing what it captured, including the username and password I typed while browsing a website. You will notice it also captures live network data, form fill data, and more.

FAQ:

Here are some FAQs on this topic. If you have a question that is not covered in this list, feel free to post a comment and I will try to answer it.

Q. Every website uses HTTPS these days, which is fully end-to-end encrypted. That means I am safe from browser extensions reading my data, right?

A. No. A browser extension sees your data before it is encrypted. It reads everything in plain text long before HTTPS comes into action.

Q. I always use a VPN. That means extensions cannot read my data, right?

A. No. Same answer as before. Extensions see everything in plain text before the VPN comes into action. Speaking of VPNs, many misunderstand what a VPN is and assume it is a security solution. It is not. Read my VPN blog here https://blog.selvansoft.com/2024/06/vpn-myth-vs-reality.html to learn more.

Q. If I only install extensions with good reviews, that means they are safe, right?

A. No. Malicious extensions often start clean to build trust, then update themselves later with harmful code once they have a large user base.

Q. If an extension is open source, that means it is safe, right?

A. Not necessarily. Most people never review the source code, and even if they do, the published code may not match the code that was actually packaged and uploaded to the store.

Q. If I install an extension from a well‑known company, I should be safe, right?

A. Usually safer but not guaranteed. Large companies have had compromised developer accounts and supply‑chain attacks. Trust helps, but it is not absolute protection.

Q. If I disable an extension on certain websites, it cannot read anything from those sites, right?

A. Not always. Some extensions request broad permissions that allow them to run everywhere, even if you manually toggle them off on specific sites.

Q. If I use private browsing or incognito mode, extensions cannot access my data, right?

A. Not exactly, but you can still grant them access. If you enable an extension in incognito mode, it has the same visibility as in normal browsing.

Q. If I uninstall a suspicious extension, I am safe again, right?

A. It stops future access of course. However, a malicious extension could have already captured data or exfiltrated information before you removed it.

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Stay Informed and Safe Online
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