The author isn't implying that the NSA intentionally injected the word "PRISM" into the header of every HTTP/2 connection. Rather, that the members of the IETF that collaborated on the standard chose to change the existing dummy text to match those initials once the existence of the program was leaked to the public, presumably as a sort of inside joke/protest.
^ I figure I'd clarify that in case anyone else gets as confused as I did about what possible political or technical objectives the NSA might achieve by including a reference to a top-secret spy program in every HTTP/2 message (although it does seem like the sort of thing a comic-book evil intelligence organization would do :P).
^ I figure I'd clarify that in case anyone else gets as confused as I did about what possible political or technical objectives the NSA might achieve by including a reference to a top-secret spy program in every HTTP/2 message (although it does seem like the sort of thing a comic-book evil intelligence organization would do :P).