CCTV footage has been released after a woman walking her dog was stabbed in the stomach in a "random" attack.
The victim, who is in her 50s, was attacked on Thursday morning in Boxhill Park, near Clifton Drive, Abingdon, Oxfordshire.
Thames Valley Police said a man in the CCTV footage may have information that could help their enquiries.
A 17-year-old previously arrested on suspicion of attempted murder has been released without further action.
Police said the attacker put his left hand over the woman's mouth before stabbing her once in the stomach.
His victim received hospital treatment but has since been discharged.
The suspect is a white male in his late teens, about 5ft 10in tall, with a slim build, wearing black turn-up denim shorts, a grey top, white and black trainers, and glasses.
Police are asking anyone in the area between 10:00 and 12:00 BST to come forward if they saw anything.
Det Insp Ali Driver described it as a "random" attack and said: "We are releasing CCTV footage of a man who we believe may have information that could assist our investigation.
"We are aware that a man may have been walking his dog not far from the incident and we would ask that man to please call as he may have witness information."