Google has removed two Chrome extensions from its store due to the way they were serving ads to users. The extensions in question, Add to Feedly and Tweet This Page, both started life as useful additions to Google's web browser, but were soon serving users pop-ups and other intrusive ads. The reason for the sudden change in behavior? In Add to Feedly's case, at least, it was purchased from its developer and quickly began serving ads to its 30,000 users.

In a blog post, Add to Feedly developer Amit Agarwal describes how he got an email presenting "a four-figure offer for something that had taken an hour to create." As you'd expect, the developer decided to cash in, but a month on realized the new owners of the extension silently updated it to serve ads. "These aren't regular banner ads," says Agarwal, "these are invisible ads that work [in] the background and replace links."

Developers have been approached to sell their extensions

The issue was picked up by OMG Chrome and Ars Technica, both of which suspect the issues aren't limited to Add to Feedly and Tweet This Page. The suggestion is that advertisers regularly buy popular extensions and transform them into adware. This appears to be backed up by the developer of the popular Honey extension, who claimed last weekend he too was approached by advertisers about selling the add-on.

Shortly after the articles were published, Google took action against the rogue extensions, citing a December change to its policies that outlaws complex changes to websites by extensions, according to The Wall Street Journal. Although the changes aren't due to be enforced until June, Google has clearly taken a harder stance on such flagrant abuse. Agarwal, for his part, admits "it was probably a bad idea" to sell Add to Feedly, and apologizes to users affected by the adware.