The ten pictures were taken by a RAF photographer, but were not cleared by the UK's Ministry of Defence before being published on the official website of the Duke and Duchess of Cambridge.
Four of the ten pictures have been taken down following the realization that they showed information that could allow attackers to access restricted MoD systems.
The various pictures showed computer screens, documents and bulletin boards in the background, some of which contained computer passwords and usernames.
The MoD reacted several hours after the pictures were put online, and instructed its technicians to reset the revealed login credentials as a precaution.
According to The Daily Telegraph, the passwords in question were related to "unclassified websites used by the pilots to calculate the amount of fuel they need for their Sea Kings and to access information on the Civil Aviation Authority's website."
The pictures have since been made available online again, but with the aforementioned details pixellated.