Browser Extensions Can Have Malware: My Shock of “The Great Suspender” Chrome and Edge Extensions

For a couple of weeks, I have been pondering whether my browser extensions could be a source of vulnerabilities. It turns out they can!

A couple of days ago, I received a notification from the Microsoft Edge browser warning me about malware in one of my extensions: The Great Suspender.

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I started panicking, so I decided I would start researching this. I found the GitHub repository for The Great Suspender extension. I searched for “malware” in the open issues and surprisingly found a relevant issue.

SECURITY: New maintainer is probably malicious

Here are a couple of snippets from the issue that increased my concerns.

On November 6th, @lucasdf discovered a smoking gun that the new maintainer is malicious.

Using the chrome web store version of this extension, without disabling tracking, will execute code from an untrusted third-party on your computer, with the power to modify any and all websites that you see.

I have been running anti-malware software and running scans daily, and there were no reports of malware. It occurred to me that anti-virus and anti-malware might only catch malware running on the machine.

Fortunately, I have been running the Malwarebytes browser extension for a few months. I hope this helped mitigate some of the issues, yet the malware might have been present since November 2019 (that more than one year ago at the time of this writing).

My actions steps

I started to take action right away.

  • I uninstalled the extension from the Microsoft Edge browser. Edge had already disabled it for me and no longer allows anyone to install it.
  • I uninstalled the extension from the Chrome browser. I also reported abuse since Chrome still allows anyone to install it.
  • I fully cleaned my browsers by clearing the all-time history, cache, etc.
  • I ran CCleaner to do a full cache clean on my machine.
  • I installed another anti-virus program and ran a full, deep scan just if my anti-malware program missed anything.
  • I started to changed passwords to my sensitive accounts.
  • I revisited my browser extension preferences, which I will discuss in further detail.

From what I can tell, there is no breach. I hope it stays that way.

Updated browser extension preferences

I did the following to improve my browser extensions:

  • I updated all the remaining extensions by visiting Manage Extensions, enabling Developer Mode, and performing an Update.
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  • I checked the extension permissions and realized I was giving the “keys of the kingdom” to all my extensions, so I put that to an end.
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  • I visited each of the extension preferences, navigated to This Can Read and Change Site Data, and set the permission to When You Click the Extension. I implemented this setting to all extensions except those meant to “protect” me, such as the Malwarebytes Browser Guard extension. Note: The screen capture below shows the restricted setting for illustration purposes.
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Now, when I want to use an extension, I need to activate it.

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The extension is currently disabled.

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It is somewhat of an inconvenience. Yet, I still benefit from the extension only when I want to use it instead of when the extension wants to do something.

Conclusion

Decide whether it makes sense to install a browser extension, whether you can trust it, and how much of your data you are willing to give away.

Consider implementing the extension settings I showed above, and visit sensitive web sites (e.g., banking sites) using Incognito Mode.

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Stay secure,
Miguel

About the Author

Miguel is a Principal Security Engineer and is the author of the " Serverless Security " book. He has worked on multiple serverless projects as a developer and security engineer, contributed to open-source serverless projects, and worked on large military systems in various engineering roles.


Originally published on Medium.com

Photo by Michael Geiger on Unsplash

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