Editors of the Hungarian Wikipedia discovered in September 2010 that 6,217 (55%) of the approximately 11,000 articles created by one of the contributors had been lifted verbatim from copyrighted reference works. This was a serious violation of Wikipedia directives as well as of basic legal and ethical norms, and is condemned by the Wikipedia community. The editor in question has voluntarily refrained from editing Wikipedia since his actions were discovered, and his sysop credentials, which, for the past few years, had authorized him to make administrative changes in the encyclopedia, were withdrawn by the community.
Since Wikipedia is freely editable, inevitably there is occasional vandalism or copyright infringement on its pages. As a protective measure, the project has an intricate filtering mechanism operated by editors who have earned the trust of the rest of the community.▼
This serious violation was eventually revealed by the editors of Wikipedia themselves, and addressing the issue has been a top priority. All the articles of the editor in question have been checked for plagiarism in a massive effort spanning several weeks and involving about a dozen editors. In the end, 5,227 articles had to be deleted, while another 424 were re-written to rectify the copyright infringements. The impacted publishers have been notified as well.
▲Since Wikipedia is freely editable, inevitably there
There is a much more detailed report on this event in Hungarian at [[WP:VILCOPY|http://hu.wikipedia.org/wiki/WP:VILCOPY]]