A 15 year old XML file created a stir in the Ruby on Rails world today as it was discovered that freedesktop.org.xml which is GPL 2 licensed was included improperly in the mimemagic project which was MIT licensed. The author accepted this notification as valid, pulled prior versions, and switched licenses [github.com] but as this was a dependency of Rails it promptly got the attention [github.com] of programmers worldwide that rely on the Rails gem for their applications.
Since Rails itself is MIT licensed this makes for a difficult day of sorting out licensing options for many people.