Spammers buy Chrome extensions and turn them into adware

Two developers who sold their popular Chrome extensions saw them misused for aggressive advertising

Changes in Google Chrome extension ownership can expose thousands of users to aggressive advertising and possibly other threats, two extension developers have recently discovered.

At least two Chrome extensions recently sold by their original developers were updated to inject ads and affiliate links into legitimate websites opened in users' browsers.

The issue first came to light last week when the developer of the "Add to Feedly" extension, a technology blogger named Amit Agarwal, reported that after selling his extension late last year to a third-party, it got transformed into adware. The extension had over 30,000 users when it was sold.

A second developer, Roman Skabichevsky, confirmed Monday that his Chrome extension called "Tweet This Page" suffered a similar fate after he sold it at the end of November.

Skabichevsky accepted an offer to sell the simple extension for $500 because he didn't have time to improve it anymore.

"A woman named Amanda who contacted me said they wanted the extension 'for further development'," Skabichevsky said via email. It was weird because the extension's code is open sourced so anyone can work on it, "but I sold it anyway, thinking it would be better for the world. I was so wrong!"

Agarwal's story is similar. He sold his extension for a four-figure sum after being contacted by a woman.

"A month later, the new owners of the Feedly extension pushed an update to the Chrome store," he said Thursday in a blog post. "No, the update didn't bring any new features to the table nor contained any bug fixes. Instead, they incorporated advertising into the extension."

"These aren't regular banner ads that you see on web pages, these are invisible ads that work the background and replace links on every website that you visit into affiliate links," Agarwal said. "In simple English, if the extension is activated in Chrome, it will inject adware into all web pages."

Converting a trusted and popular extension into an aggressive advertising tool is more efficient for adware pushers than creating an extension from scratch and building a large user base they can later target, because it brings a quicker and most likely bigger return on investment.

The "Add to Feedly" and "Tweet This Page" extensions have been removed from the Chrome Web Store this weekend, supposedly by Google. However, the company did not immediately respond to a request for comment.

It's not clear if any other extensions from the Chrome Web Store were resold and exhibit the same behavior.

According to the Chrome Web Store developer program policies, advertising is allowed in apps hosted in the store, but there are strict criteria for displaying ads on third-party websites: the behavior needs to be clearly disclosed to the user, there needs to be clear attribution of the ads' source, the ads must not interfere with any native ads or functionality of the website and the ads must not mimic or impersonate native ads or content on the third-party site.

Chrome extensions are generally updated in the background without user interaction, unless their permission requirements change. The problem is that many installed extensions already have the permission allowing them to modify content on Web pages visited by users.

In the two reported cases the existing extensions were modified and used for aggressive advertising. However, the same technique can be used for more nefarious purposes.

"They could do worse like creating spam tweets on behalf of the extension users, or steal information from opened web pages," Skabichevsky said. "The extension was using my old Twitter API keys and I just reset them."

Using extensions to distribute malware directly is unlikely because Chrome scans downloaded binaries and flags the suspicious ones, said Zoltan Balazs, the CTO of IT security research firm MRG Effitas, via email. Even if they pass the scan, launching malicious binaries automatically would only be possible through a Chrome zero-day exploit and finding such an exploit is not a trivial task, he said.

Balazs researched the security risks posed by browser extensions before and even released proof-of-concept malicious extensions.

"My opinion is that dropping traditional malware is not a real threat here, but performing form injection, password stealing, cookie stealing for bypassing two factor authentication, credit card information stealing and launching distributed denial-of-service attacks using the browser as a proxy are actions that can be done via malicious extensions," he said. "I believe criminals buy extensions that already have a lot of permissions."

"Chrome add-ons can inject scripts into web pages so they can possibly do nasty things though there are no known case of them spreading malware yet," Agarwal said Monday via email.

The developer believes there should be an audit process in place on the Google Chrome Web Store like there is on the Mozilla Add-ons repository. There should also be a feature that allows users to figure out what a particular extension does to the websites they visit, he said.

Join the newsletter!

Error: Please check your email address.
Rocket to Success - Your 10 Tips for Smarter ERP System Selection

Tags applicationsonline safetyGooglesecurityMRG Effitasbrowserssoftwarescamsmalwareprivacy

Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Lucian Constantin

IDG News Service
Show Comments

Cool Tech

SanDisk MicroSDXC™ for Nintendo® Switch™

Learn more >

Breitling Superocean Heritage Chronographe 44

Learn more >

Toys for Boys

Family Friendly

Panasonic 4K UHD Blu-Ray Player and Full HD Recorder with Netflix - UBT1GL-K

Learn more >

Stocking Stuffer

Razer DeathAdder Expert Ergonomic Gaming Mouse

Learn more >

Christmas Gift Guide

Click for more ›

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Walid Mikhael

Brother QL-820NWB Professional Label Printer

It’s easy to set up, it’s compact and quiet when printing and to top if off, the print quality is excellent. This is hands down the best printer I’ve used for printing labels.

Ben Ramsden

Sharp PN-40TC1 Huddle Board

Brainstorming, innovation, problem solving, and negotiation have all become much more productive and valuable if people can easily collaborate in real time with minimal friction.

Sarah Ieroianni

Brother QL-820NWB Professional Label Printer

The print quality also does not disappoint, it’s clear, bold, doesn’t smudge and the text is perfectly sized.

Ratchada Dunn

Sharp PN-40TC1 Huddle Board

The Huddle Board’s built in program; Sharp Touch Viewing software allows us to easily manipulate and edit our documents (jpegs and PDFs) all at the same time on the dashboard.

George Khoury

Sharp PN-40TC1 Huddle Board

The biggest perks for me would be that it comes with easy to use and comprehensive programs that make the collaboration process a whole lot more intuitive and organic

David Coyle

Brother PocketJet PJ-773 A4 Portable Thermal Printer

I rate the printer as a 5 out of 5 stars as it has been able to fit seamlessly into my busy and mobile lifestyle.

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?