Abi, 19, was taken to hospital by ambulance after she fell down a set of stairs at the studios while waiting to find out if she had made it through to next week's show.
The hopeful was strapped to a stretcher and given an oxygen mask before being carried out by paramedics.
As a result, Abi did not appear on The X Factor's spin-off show, The Xtra Factor, leaving presenter Caroline Flack to explain her absence.
Caroline told viewers: "She has actually hurt her back so she has gone to have her back checked.
"She is absolutely fine. I think she's going to be ok."
A spokesman for The X Factor has since told Reveal that Abi has now returned to the contestants' house.
"Abi Alton went to hospital as a precaution after Sunday night's show having slipped on some stairs backstage. She has since returned to the X Factor house," he said.
Abi's accident came just a day after pregnant Miss Dynamix singer SeSe Foster was taken to hospital, meaning the girl group could not perform on Saturday night's show.
SeSe, 22, fell ill while rehearsing with bandmates Jeanette Akua, 21, and 16-year-old Rielle Carrington.
After being checked over, SeSe - who is six months pregnant - assured fans that her baby was fine and explained that she had actually suffered an anxiety attack.
Speaking after she was released from hospital, SeSe said: "In case some of you are misunderstood, it was nothing to do with me being pregnant.
"I had an anxiety attack and it's happened a lot in my life. My baby's fine, the heart rate is lovely. I just need to calm my nerves before performing."
Miss Dynamix were given an automatic pass through to next week's show.
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