The spy code installed in addition to the browser programs Chrome and Firefox causes the browsing history to be recorded and stored in a database, DN writes.

It has been possible to see exactly what people have done online, and although the information is said to be anonymous, it has been possible to identify both people, places and events. For example, DN has been able to take part in the handling of a staff case at a Swedish company, as well as school staff who handle cases about named Swedish students.

- There were usernames, passwords and email addresses and also information that could negatively affect companies, says David Jacoby to SVT.

The expert: "Can see everything"

- The companies that collect data can see everything. Even patient data, Sam Jadali, the IT security expert who revealed the leak, tells DN.

The information was sold by the company behind the database, Nacho Analytics, which, however, was closed after the leak was revealed. Surf patterns are a way of studying customer patterns and monitoring competitors. The leak is similar to what came from the scandalous company Cambridge Analytica, which could abuse Facebook data for political campaigns.

The programs have been deleted

The add-ons that contained the spy code, the biggest ones being Hover Zoom, Speakit! and Fairshare Unit, have been removed from Google and Firefox web stores after the disclosure.

However, according to David Jacoby, this leak is not entirely unique in practice, and he believes that there are still several companies and organizations that "collect a lot of information" all the time.

- If you arrest ten drug addicts, does the drug disappear? No, obviously it doesn't, Jacoby says.