Yesterday, noted security researcher (and Google employee) Tavis Ormandy published his discovery that Ubisoft's UPlay DRM installs a browser plugin that leaves your computer terribly vulnerable to drive-by attacks over the Internet. The plugin is meant to allow Ubisoft to start games on your computer over the Internet, but it lacks an effective authentication mechanism. This means that an attacker could check your browser to see if you have Ubisoft's DRM installed, and if it finds it, cause the plugin to run malicious software that hijacks your computer.
An early report on Hacker News characterized this as a "rootkit," which triggered a long (and tedious) debate about the formal definition of rootkits and whether Ubisoft's system qualified. To me, this seems rather beside the point, which is that Ubisoft's overall installation process involves a high degree of secrecy and obfuscation, because none of Ubisoft's users want DRM (some may not mind it, but it's a rare gamer who says, "Please install software on my computer that watches what I do and orders my computer to prevent me from doing things that displease a distant corporation"). As a result, security vulnerabilities that arise from sloppiness (or malice) are more difficult to discover and to put right.
PC Gamer got a rare and terse quote from Ubisoft on the issue, in which the company says it is "looking into" the issue, later updated with the statement that a "forced patch" has been issued to fix the issue (though this claim hasn't been independently verified by any source I can find).
There's more commentary on TorrentFreak, which places the DRM in context -- "seen as an essential part of life for many games developers." The Slashdot thread on the issue is lively, but also full of deeply misinformed legal speculation about which laws Ubisoft may or may not have broken in the process.