Following the discovery and prompting of a security researcher at Awake Security, Google says it has removed 106 malicious Chrome extensions that had 32 million downloads, and which were gathering browsing history and sensitive credentials from users.
They don't yet know who was behind the malware effort.
"When we are alerted of extensions in the Web Store that violate our policies, we take action and use those incidents as training material to improve our automated and manual analyses," Google spokesman Scott Westover told Reuters.
Most of the free extensions purported to warn users about questionable websites or convert files from one format to another. Instead, they siphoned off browsing history and data that provided credentials for access to internal business tools.
Based on the number of downloads, it was the most far-reaching malicious Chrome store campaign to date, according to Awake co-founder and chief scientist Gary Golomb.
Google declined to discuss how the latest spyware compared with prior campaigns, the breadth of the damage, or why it did not detect and remove the bad extensions on its own despite past promises to supervise offerings more closely.