A "blunder" by the City of Sydney Council has caused floor plans of high-security Local Court holding cells to be posted online.

The Sydney Morning Herald this morning reported that the document, stamped "commercial in confidence" and "for council use only" appeared on the Council's development application web site.
The document, which has since been removed, accompanied an application for the $2.6m refurbishment of existing holding cells at the Sydney Central Local Court.
According to the Herald, it detailed the location of the 12 holding cells, interview rooms, guards' post, gun safe and prisoner loading dock.