Exactly at extra op 49 the second area where you can't reach the second floor in underground passage towards peacewalker hangar.
I've googled it a thousand times but nobody seems to have mentioned it anywhere.
if you have a soldier with channeler skill, you can easily find it but you can't get it unless you play coops, I think.
And I can't load up my inventory with two cardboard boxes. If I try to load rescue box along with lovebox, the first box disappears in "mission prep" screen
For getting this design spec, you must have two boxes or a coop teammate to reach the second floor.
as soon as you enter the second area after accessing the elevator, turn right and you'll find a big metal box. use a cardboard box to climbit and them if you look closely, yo can see the confidential document on top.
Tried to find any cardboard boxes with soldiers by holdup and checking but to no avail.
This is frustrating. I don't know what that document is for(may be a special secret weapon that can kill monsters with one shot? I'm eager.)