The UK Ministry of Defence has published a classified government report on its website that contained blacked out parts that were unfortunately visible when doing a straight forward copy/paste.
The mistake was discovered by UK newspaper the Dailystar and they alerted the MoD which confirmed that the "schoolboy error" was indeed genuine.
Whoever edited the PDF document thought that just turning the text background black would be enough to make the words unreadable.
Although the Daily Star stressed that it will not publish any information that could jeopardise Britain's national security, it did mention that the blanked out paragraphs included details of potential weaknesses in the UK nuclear submarine fleet.
The Daily Star quotes one senior MoD official saying, “This is hugely embarrassing. Whoever is responsible should be sacked. The Americans will be furious their procedures have been exposed.”
The report was posted on the UK Parliament's website after an anti-nuclear campaigner made a a Freedom of Information request.
The redacted, declassified document, entitled "Safety Regulators' advice on the selection of the propulsion plant in support of the future deterrent review note," can be viewed here.