Since when does pasting screenshots with CTRL-V work universally in the browser and what kind of voodoo makes it possible?

Since not so long I noticed that after making a screenshot in my Debian it was telling me I could paste it from the clipboard and it works here in snort and in GitHub and in many places. Does my system emulate a drag-and-drop of the file? Since when does that work in Debian? Is this an old UI on other OSs?