Things you learn every day...

So I was trying to make some VERY fake money for a party one of my friends is having, and of course, the first thing I did was to download an image of money to use as a template. To my surprise, when I open it in Adobe Photoshop, I get the following message:


Now, is this something that was added to this file, or is Photoshop so incredibly smart that it can automatically spot a dollar bill?
Either way, it was a very interesting message that I've never seen before...