Authorities responded to Westfield MainPlace at about 5:15 p.m. Wednesday. The woman said she was getting in her car when a suspect pushed her into the vehicle. He allegedly brandished a weapon and sexually assaulted her.
The woman was able to escape and get into the car of another shopper, who called police. The suspect took some of the victim's belongings before fleeing the scene.
Detectives are reviewing images from surveillance cameras in the area. A suspect description was not immediately available.
Westfield MainPlace said in a statement, "Safety of our customers is paramount, but we are deferring everything to Santa Ana (police)."
Police advised holiday shoppers to always be aware of their surroundings.
"If you have your cellphone with you, carry it in your hand close to your person," said Santa Ana Police Cpl. Anthony Bertagna. "If you have the chance, shop with a buddy. If you're uncomfortable, ask security, ask the officers."
Bertagna said there would be heightened security at the mall because of the incident.
Anyone with information is urged to call Orange County Crime Stoppers at (855) TIP-OCCS.