(credit: Chrome )

Users of Google’s Chrome browser have faced three security concerns over the past 24 hours in the form of a malicious extension with more than 2 million users, a just-fixed zero-day, and new information about how malware can abuse Chrome's sync feature to bypass firewalls. Let’s discuss them one by one.

First up, the Great Suspender, an extension with more than 2 million downloads from the Chrome Web Store, has been pulled from Google servers and deleted from users’ computers. The extension has been an almost essential tool for users with small amounts of RAM on their devices. Since Chrome tabs are known to consume large amounts of memory, the Great Suspender temporarily suspends tabs that haven’t been opened recently. That allows Chrome to run smoothly on systems with modest resources.

Characteristically terse

Google's official reason for the removal is characteristically terse. Messages displayed on devices that had the extension installed say only, “This extension contains malware” along with an indication that it has been removed. A Google spokesman declined to elaborate.

Enlarge (credit: Getty Images )

In December, Ars reported that as many as 3 million people had been infected by Chrome and Edge browser extensions that stole personal data and redirected users to ad or phishing sites. Now, the researchers who discovered the scam have revealed the lengths the extension developers took to hide their nefarious deeds.

As previously reported, the 28 extensions available in official Google and Microsoft repositories advertised themselves as a way to download pictures, videos, or other content from sites including Facebook, Instagram, Vimeo, and Spotify. Behind the scenes, they also collected user’s birth dates, email addresses, and device information and redirected clicks and search results to malicious sites. Google and Microsoft eventually removed the extensions.

Researchers from Prague-based Avast said on Wednesday that the extension developers employed a novel way to hide malicious traffic sent between infected devices and the command and control servers they connected to. Specifically, the extensions funneled commands into the cache-control headers of traffic that was camouflaged to appear as data related to Google analytics, which websites use to measure visitor interactions.

Enlarge (credit: Getty Images )

As many as 3 million people have been infected by Chrome and Edge browser extensions that steal personal data and redirect users to ad or phishing sites, a security firm said on Wednesday.

In all, researchers from Prague-based Avast said they found 28 extensions for the Google Chrome and Microsoft Edge browsers that contained malware. The add-ons billed themselves as a way to download pictures, videos, or other content from sites including Facebook, Instagram, Vimeo, and Spotify. At the time this post went live, some, but not all, of the malicious extensions remained available for download from Google and Microsoft.

Avast researchers found malicious code in the JavaScript-based extensions that allows them to download malware onto an infected computer. In a post , the researchers wrote:

Enlarge / Photo illustration by Jakub Porzycki/NurPhoto via Getty Images (credit: Getty Images)

A US senator is calling on the Department of Homeland Security’s cybersecurity arm to assess the threat posed by browser extensions made in countries known to conduct espionage against the US.

“I am concerned that the use by millions of Americans of foreign-controlled browser extensions could threaten US national security,” Senator Ron Wyden, a Democrat from Oregon, wrote in a letter to Christopher Krebs, director of the DHS’ Cybersecurity and Infrastructure Security Agency. “I am concerned that these browser extensions could enable foreign governments to conduct surveillance of Americans.”

Also known as plugins and add-ons, extensions give browsers functionality not otherwise available. Ad blockers, language translators, HTTPS enforcers, grammar checkers, and cursor enhancers are just a few examples of legitimate extensions that can be downloaded either from browser-operated repositories or third-party websites.