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The woman was spotted slumped up against a tree in low bushes in what appears to be a busy built-up area.
Photos shared on Chinese social media site Weibo claimed to show the woman before and after the attack, and reveal how horrifically transformed her face was by the force of the blows.
Reports circling on Weibo claimed the woman was actually attacked by four men hired by the cheating man's wife.
The posts alleged she had been detained and beaten for several days.
The woman has refused to reveal how she suffered the injuries, the public security bureau of the city of Anqui in Shandong Province said on its Facebook page.
Chinese news service Shen Weifang suggested the images of the woman before the attack were ripped from one of her social media accounts.
One of the woman's selfies which surfaced on social media came with the caption: "I am only in my twenties, but I am feeling more and more tired.
"People do not understand my story.
"I have witnessed a thousand kinds of sorrow."
An Apple Daily reader commented: "It might be immoral to be a mistress, but such violence is not tolerable.
Another offered sympathy and said: "She got badly wounded. It might affect her life forever."