The Ministry of Defence in Britain has admitted secret information about its nuclear-powered submarines was published online by mistake.
The ministry had blacked out key sections of a report, but a technical error meant they could be read by anyone who copied and pasted them into a new document.
The BBC reports the data revealed how British submarines would try to withstand catastrophic accidents.
The ministry said a secure version had now been published and it was working to stop such an incident happening again.
The Daily Star Sunday reported the information also included measures used by the US Navy to protect its nuclear submarines