The offence occurred between 2am and 3am yesterday when a stranger entered a home in the Haywra Court area, off Haywra Street.
He assaulted a woman aged in her early 60s inside the home, causing bruising to her face.
The culprit then stole wallets and mobile phones, officers said.
He is described as white, aged 20 to 30, about 5ft 6ins tall and he was wearing a dark, or possibly green, hooded top.
Detective Constable Paul Smith, the investigating officer, said: “This is a particularly heinous crime which subjected the victim to a terrifying experience. She is being supported by the police and measures have been put in place to enhance security at the property.
“Police patrols have also been stepped up in the area to provide reassurance to the local community while enquiries continue into what appears to be an isolated but very disturbing incident.”
DC Smith added: “I am appealing for people to come forward with any information about suspicious activity in the area of Haywra Court at the time of the incident or in recent days.
“In particular, we need to know about possible sightings of a man in a dark hooded top who matches the description given.
“Even the smallest piece of detail could be vitally important to the investigation.”
If you can help, please call North Yorkshire Police on 101 or email [email protected]
Alternatively, contact Crimestoppers anonymously on 0800 555111.
Quote reference number 12180147093.