Harvard Business School professor Ben Edelman uncovered and publicised the error in his blog. Google responded soon after with a statement to say that tracking would only continue until the user restarts the browser.

“Once the user restarts the browser, the issue is no longer present,” the search giant said. “A fix that doesn’t require a browser restart is now available on www.google.com/toolbar and in an automatic update to Google Toolbar that we are starting [today].”

Edelman previously investigated the retailer Sears for failing to properly notify customers who signed up to a research community that it was installing tracking software on their computers.

• In other online privacy news, the New York Times reports on the development of a new icon that advertisers are set to adopt as a way to inform people when behavioural targeting is being used to serve them ads, with the ability to click through to an explanation of how targeting works. The hope is such an initiative will stave-off regulatory threats, which potentially risk curtailing the ability of companies to track web behaviours for research purposes.