Google has started removing ad-injecting extensions for its Chrome browser after it discovered as many asthat exposed Millions of its users to malicious software and fraudulent activities. Over 5 percent of users visiting Google websites are infected by at least one ad injector. Google received more than 100,000 complaints from its Chrome users about ad injection, which is far more than what the company receives for network errors, performance problems, or any other issue. Google is also making changes to its AdWords policies in order to prevent advertisers from offering users shady downloads.
Source: https://thehackernews.com/2015/04/ad-injectors-chrome-extensions.html