Chrome Extensions with Hidden Backdoors: How to Spot and Remove Them

When you install a browser extension to help with scheduling, grammar, or note‑taking, you expect it to do one thing well. You probably don’t expect it to read your email, watch every site you visit, or phone home with your credentials. But that is exactly what a growing number of “productivity” extensions have been doing in 2026.

Security researchers at Security Boulevard documented one such campaign in March, where seemingly legitimate tools turned out to be backdoors. The FBI has since opened an investigation into related hacks, underscoring that even government systems are being targeted. For the average user, the risk is lower but still real: a single malicious extension can expose your passwords, banking sessions, or corporate accounts.

This article explains how these backdoors work, why they are hard to spot, and what you can do right now to clean up your browser.

What happened: productivity tools with a hidden payload

According to the Security Boulevard report, attackers submitted Chrome extensions to the Chrome Web Store that promised minor productivity boosts — a calendar helper, a PDF merger, a grammar checker. After installation, the extensions requested broad permissions: access to all websites, ability to read and change data on visited pages, and in some cases, access to browser storage.

The extensions then connected to remote servers controlled by the attackers. Once connected, they could:

  • Steal session cookies – allowing an attacker to impersonate the user on logged‑in services.
  • Inject keyloggers – capturing passwords typed into forms.
  • Exfiltrate internal network data – especially dangerous in enterprise environments where the browser might have access to company web apps.

The campaign was sophisticated enough that many extensions evaded automated scans. They were distributed through the official store, sometimes with hundreds of five‑star reviews from accounts that may have been fabricated.

Why it matters

For a home user, a backdoored extension can mean identity theft or drained bank accounts. For enterprise employees using the same browser for work, the consequences can be far worse. Many companies allow Chrome extensions for day‑to‑day tasks, and IT departments rarely audit every add‑on. A single compromised extension can become a foothold for lateral movement inside a corporate network.

The FBI investigation mentioned in the same Security Boulevard article suggests that threat actors are now applying these techniques against government targets. That means the tools are becoming more professional and harder to detect.

What readers can do: a practical audit guide

You don’t need advanced technical skills to reduce your risk. Follow these steps to review your Chrome extensions and remove suspicious ones.

1. List all installed extensions

Open Chrome, click the three‑dot menu → Extensions → Manage Extensions. You will see every extension you have installed, whether enabled or disabled.

2. Check the permissions

Click Details on any extension. Look at the list under “Permissions.” Watch out for:

  • “Read and change all your data on all websites” – Most single‑purpose tools do not need this. A grammar checker only needs to see the text fields you are typing in, not every page you browse.
  • “Access your browsing history” – A calendar helper does not need to know which sites you visited last week.
  • “Manage your apps, extensions, and themes” – This permission lets an extension install or remove other extensions. Legitimate tools rarely require it.

If an extension has permissions that seem excessive for its stated function, treat it as suspicious.

3. Verify the developer and reviews

Check the publisher name. Is it a known company? Does the developer have a website? Look for reviews that mention privacy or security concerns, not just generic praise. If the extension has many five‑star reviews but a small number of installs, that may be a red flag.

4. Look at the update date and version history

Extensions that have not been updated in over a year are riskier, but recent updates alone are not a guarantee. If an old extension suddenly received a flurry of updates that added new permissions, that is worth investigating.

5. Remove anything you don’t need

For each extension, ask: “Did I actively install this? Do I use it regularly?” If the answer is no, remove it. Disable extensions you rarely need, then remove them if you don’t miss them.

6. Reset permissions for ones you keep

You can often revoke the “all sites” permission after an extension asks for it. In Chrome, you can set an extension to only run when you click its icon, rather than on every page. This limits its attack surface.

7. Use Chrome’s built‑in safety tools

Chrome now includes a “Safety Check” under Settings → Privacy and Security. Run it periodically. It will flag extensions that have been removed from the store, that are requesting unusual permissions, or that are known to be harmful.

Choosing safer extensions going forward

  • Stick to the official Chrome Web Store – sideloaded extensions from random websites are far more dangerous.
  • Prefer extensions from reputable publishers – established companies like Google, Microsoft, or well‑known open‑source projects are less likely to serve malware.
  • Read the privacy policy – if one exists. Many free extensions have vague policies that effectively allow them to sell your data.
  • Limit the number of extensions you install – each one adds risk. A lighter browser is also faster and more stable.

Sources

There is no perfect way to guarantee a Chrome extension is safe, but with a few minutes of due diligence you can dramatically reduce your exposure. If you find an extension you are unsure about, remove it. The convenience of a tool is not worth handing over control of your browser.