GamesIndustry.biz are reporting that Ubisoft accidently put a confidential 2GB file on their public ftp which contained artwork and screenshots for some of their upcoming titles. This included media for the unannounced Splinter Cell: Conviction and FarCry 2 (a tech demo for FarCry 2 was downloadable).

The files have since been removed and Ubisoft are taking efforts to ensure such a leak doesn't happen again.

** Update **
Here's a brief UbiSoft statement on the matter.

We are clearly displeased that confidential information from Ubisoft has been distributed on the internet. The publication of this type of information can only be harmful to the game development process and we will take all steps necessary to prevent this from happening in the future. We are still investigating the events that lead to this information leak and at this time have no further comment.

Full list of titles included in the file:

Assassins Creed
Far Cry 2
Far Cry PSP
Far Cry Wii
Lost
Naruto 360
Open Season
Prince of Persia 4
Rainbow 6: Vegas
Rocky PSP
Splinter Cell Conviction
Surf's Up
Star Wars PSP
Shaun White Snowboarding
Teenage Mutant Ninja Turtles
Teenage Mutant Ninja Turtles GBA