In September 2012, a user at the Ownedcore forums reported that they appeared to have discovered a digital watermark reportedly embedded in all client generated screenshots since Patch 2.1 as part of an in-game screenshot utility. The information in the watermark reportedly includes the account ID (email address?), a timestamp and the IP address of the current realm, but does not the account password, the IP address of the user, or any personal information like name/surname, etc.
It is not clear if the information encoded in this watermark has been independently confirmed by anyone outside some Ownedcore forum users. However, this story has been picked up by many news outlets, but with very little or no follow up. Some reports have speculated that this technology is similar to that provided by a company called Digimarc.
Since most Mac OS X players likely use the OS key shortcut (Cmd-Shift-3 or Cmd-Shift-4) to make screenshots, they would not be affected by this technology.