The guys at OwnedCore forums discovered that all World of WarCraft screenshots contain user’s private information embedded (hidden) in them.
After three days of working cooperatively, the forum members proved without doubt that all their WoW screenshots taken since 2008 contain this invisible watermark. The watermark includes user ID, the time the screenshot was captured and the IP address of the server he was on at the time.
The watermark doesn’t contain the user real name or account password, but it can be used to link the screenshot to the user account and to the server he is playing on, thus allowing Blizzard to track private servers. Inadvertently, it also allows hackers and scammers to figure out which characters belong to which account and to plan their scam accordingly.
The World of WarCraft Terms of Service agreement doesn’t mention this practice anywhere.
Interestingly, if you set your screenshot quality to maximum, the watermark is not embedded in it. If you still play World of WarCraft, you can set your screenshots quality to max by typing: /console SET screenshotQuality "10".
A tool that stops WoW client from embedding the watermark in lower quality screenshots has already made its way to the intertubes, but we don’t recommend using it since it violates the EULA and might be detected as a hacking or cheating attempt. There is no need to take the risk when a single line is enough to fix the problem.