A company is going around buying abandoned Chrome extensions from their original developers and converting these add-ons into adware.

This scheme came to light two days ago when the users of a popular Chrome extension began complaining about an update that requested two intrusive permissions that the extension never used, or would have never had a reason to. The two permissions are:

Read and change data on (all) websites visited

Manage apps, extensions, and themes

The Chrome extension in question is named Particle (formerly known as YouTube+) and is a simple tool that allows users to change the UI and behavior of some of YouTube's standard features.

Back in May, the extension's original author announced it was planning to abandon the Particle Extension and build a new one called Iridium. The original author cited an upcoming YouTube UI update that would have broken most of Particle's features, hence the reason he decided to start a new project from scratch.

Extension sold to new developer

Somewhere between May and two days ago (July 11), the original author was approached by a company that offered to buy the extension from him for a price of his choosing.

The original author says he couldn't resist this offer for an extension which he deemed abandoned, so he decided to sell. Before selling, he claims he researched the buyer before approving and says he wasn't able to find any "warning signs."

The terms of the sale also include a non-disclosure agreement that now prevents the original author from revealing the company's name.

After the Particle code had changed hands, two days ago, the new owner released a Particle update through the Chrome Web Store.

Immediately, users noticed the extension's new permissions and flocked to the original author's GitHub repo to complain about the update, only to discover that the extension changed devs without any warning to existing users.

Extension pumped with code to inject ads into websites

An analysis of the Particle source reveals that the new owner added a folder named "algoad" to the original extension's code.

This new code injects ads in websites such as Google, Yahoo, Bing, Amazon, eBay, and Booking.com. Both Bleeping Computer and Particle users who analyzed the code saw the same malicious behavior. Bleeping Computer also asked two security researchers from Emsisoft to analyze the extension's code, and both confirmed the initial assessment.

New extension owner linked to similar adware-like extensions

The extension's new user — roberthawkinsg — is also the author of two other Chrome extensions: "Typewriter Sounds" and "Twitch Mini Player."

Visiting the Reviews section of all these extensions we find the same complaints about how a formerly harmless add-on turned into adware.

Particle complaints Typewriter Sounds complaints Twitch Mini Player complaints

At the time of writing the Particle extension has just over 31,000 users, the Typewriter Sounds extension has nearly 40,000 users, and the Twitch Mini Player extension has nearly 20,000 users.

In the meantime, the original author of the Particle Chrome extension is recommending that users install a Userscript version of the Particle extension, or wait until the new Iridium extension is released.