Google has removed two Chrome extensions from its web store after it was discovered that they were serving unauthorized ads in violation of the company’s terms of service. Both “Add to Feedly” and “Tweet This Page” contained hidden code that served “undesirable” ads to their users while they were browsing the web, The Wall Street Journal reports.

Google first started its crack down on Chrome extensions last December. The search giant now states that all extensions must have “a single purpose that is narrow and easy-to-understand.” But the two banished extensions, which both had less than 100,000 users each, inserted ads into web pages in places where there should have been no ads.

They weren’t always bad extensions, however. Add to Feedly, which was developed by Amit Agarwal, contained no adware until it was purchased for a four-figure sum. A month later, its new owners quietly updated the extension to incorporate advertising without making it known to users.

“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 explained on his website. “In simple English, if the extension is activated in Chrome, it will inject adware into all web pages.”

Tweet This Page was also purchased before it was updated. Both extensions had five-star reviews before they showed ads, but they quickly fell to one-star reviews after being updated. Of course, that won’t stop the new owners from showing ads to make a quick buck.

• SourceThe Wall Street Journal