A "security glitch" led to pornographic images appearing on an electronic information sign, a council has said.
The screen, in Telford, Shropshire, was photographed on 4 September showing an adult website.
Telford and Wrekin Council apologised and said a member of the public was able to display the pictures using the sign's interactive screen, normally used to search for visitor information.
The picture was sent to news website Telford Live and widely shared online.
The authority said: "We are sorry our security settings were unable to stop this on this occasion."
The council said the content had only been displayed for a short period of time but expressed "concern" the picture was shared subsequently on social media.
The sign is at the town's Southwater development which includes a mix of bars, restaurants and entertainment complexes, along with Southwater One, home to a new library, and council offices.
"A thorough review of security settings is being undertaken to seek to ensure inappropriate content cannot be accessed in future," the council said.
It said it had alerted police to the incident.
West Mercia Police said nobody had been arrested and inquires were ongoing.