Yes, that headline is true. Activision is attempting to track down the mysterious person who leaked the cover art of the next Call of Duty by issuing subpoenas to Reddit. Whether or not these subpoenas are going to have any actual effect is more of an open question; certainly Activision wants Reddit’s owners to do something, but technically Reddit never hosted the images in question and the thread simply linked to the image hosted elsewhere.
It turns out this sort of situation does actually have legal precedent, which is actually on Reddit’s side following an issue with a former Jehovah’s Witness remaining anonymous. Activision has been having no small number of issues with leaks regarding new Call of Duty content, including the upcoming battle royale mode getting leaked, which means one can understand why the company would want to find out who’s responsible for all of these internal leaks; unfortunately for the company, this may not be the path to doing so.