The woman, who has not been identified, climbed down a fence, over a wide hedge full of thorns and got past a concrete wall before swan diving into the murky moat where the polar bears swim.
One of four bears in the enclosure bit the woman's arms, legs and back before keepers rescued her out with a life preserver.
The woman was taken to Berlin's CharitÄe hospital for treatment and is still recovering, the Bild newspaper reported Monday. The hospital did not return phone calls seeking comment.
It was not clear what made the woman circumvent all those security measures and jump in with four large, fully grown polar bears. Police did not provide any motive for the incident.
Last year, a man who said celebrity polar bear Knut looked "lonely" hurdled over a water-filled ditch into his enclosure at the same zoo. The 37-year-old emerged unscathed after keepers lured Knut away with a leg of beef.
An older bear attacked Friday's leaper.
Despite visitors' repeated attempts to hug the huge, powerful bears, keepers have no plans to change the zoo's setup. The concrete wall protecting the polar bears' enclosure will not be built up higher than its current three feet (90 centimeters), nor will more guards be posted, Kloes said.
"People who want to jump in will always find a way," he added.
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