Continuity mistake: At the beginning, inside the hotel room in Hong Kong. Before Snowden puts the two cellphones belonging to his guests in the microwave, there are already two different cellphones lying in there. After the point of view switches to the microwave's turntable, the two original cellphones have magically disappeared.
Factual error: There would be no room for a thumb drive inside of a real Rubik's Cube due to the way they are constructed. When dismantled, the individual moving parts are quite small. It would certainly be possible to construct a facsimile of a Rubik's Cube that would have enough room, but it wouldn't be a fully functional puzzle the way it was in the film.