Are you running an Insider Dev build? If so, that's an exprimental feature first seen in build 25120. It is only enabled for some Insiders.Recently, a search box has been added on top of every photo. This is very irritating. Is this microsoft again making life irritating?
Windows Insiders who use the Dev Channel may get to try out new ideas, longer lead features, and experiences that are intended to help validate concepts. Starting with this preview build, some Insiders will see one of these conceptual features as we begin to explore exposing lightweight interactive content on the Windows desktop. Today, Windows exposes this type of content in the Widgets board. To begin assessing this general idea and interaction model, the first exploration in this area adds a search box displayed on the desktop that enables you to search the web.
You can remove the search box by right-clicking the desktop, selecting "Show more options" and toggling off "Show search."
If you choose to run the Insider Dev channel builds you must expect MS to try out new features such as this. It the price you pay for being an Insider, you've effectively volunteered to be a guinea pig...Found it, right click on the desktop and uncheck "show search."