Two cars were damaged by paint in Canon Street, Kettering, in the early hours of Monday (December 29).
The incident happened sometime between 2.50am and 3.50am, when the offender painted an offensive word on the passenger-side window of a Volkswagen Golf.
A nearby car was also splashed with paint.
The offender is described as a white man, aged 40 to 50, with a medium build and wearing dark clothing and a baseball cap.
Witnesses, or anyone with information, are asked to call Northamptonshire Police on 101. Alternatively, they can call Crimestoppers on 0800 555111.
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