The breach included usernames, user IDs, email addresses and passwords, and the firm has asked registered members to change their passwords.

Freecycle is a non-profit organisation that coordinates a worldwide network of ‘gifting’ groups in a bid to divert reusable goods from landfills.

The firm said the breach has been closed and it has been reported to the Information Commissioner’s Office (ICO) in the UK and authorities in the US.

In a post on its site, it said: “On August 30th we became aware of a data breach on Freecycle.org. As a result, we are advising all members to change your passwords as soon as possible. We apologise for the inconvenience.”

According to Bleepingcomputer.com, a hacker offered up the data for sale on a hacking forum in late May, although the source of the breach was only discovered last Wednesday.

An analysis of the breach showed that hackers were able to gain access to the credentials of Freecycle founder and executive director...