Facebook’s software for letting users download their data inadvertently exposed the contact information of 6 million users, the company said in a post on its security blog. Phone numbers and email addresses that are stored as part of its friend-recommendation algorithms were inadvertently attached to their contacts’ Facebook accounts, so that someone downloading an archive through Facebook’s Download Your Information tool may have received other people’s information. Facebook noted that the information was not necessarily accurate or up-to-date. The company has not received any complaints that users’ information was used maliciously, it said. In most cases, a person’s contact information was only downloaded “once or twice,” according to Facebook. Developers and advertisers cannot use the tool and therefore did not receive any contact information.