While the DC Extended Universe lends heavily from the source material, aspects of the characters and storylines have been changed to suit Warner Bros.' vision of the characters -- this includes Cyborg's origin, which has been changed drastically.
In the comics, Cyborg has two definitive origins -- depending on when you've read about the character. The pre-Flashpoint origin story sees Victor Stone experimented on regularly by his parents, who just happen to be scientists at S.T.A.R. Labs. One of their experiments actually brought a harmful being into their dimension, and upon returning the creature to its own dimension, Victor is hurt and his mother is killed. Victor is turned into a cyborg to keep him alive.
In the post-Flashpoint origin of the character, it's not that different -- instead of a creature wounding Victor, it's an explosion from a Father Box that does the damage. Whilst the DC Extended Universe keeps some aspects of this origin in place, it's changed quite a bit too. This revelation came from a recent event in the Philippines, where an image containing his new origin was posted on Twitter.
A new cause of injury leads to Victor becoming Cyborg, and it's a car crash. "Part man, part machine, Victor Stone is a former star athlete at Gotham City University," the image reads. "After a horrific car accident nearly cost his life, he was saved when his father, scientist Silas Stone, used an Apokoliptian Mother Box to reconstruct his body."
"In the process, Silas turned Victor into a human computer, organic with biomechatronic body parts. In other words, a cyborg," it continued. This origin was partly explored in Batman v Superman: Dawn of Justice, where Bruce saw Victor's body merged with one of three Mother Boxes that are on Earth. So whilst this origin isn't miles away from the ones known in the comics, it doesn't mean that Warner Bros. isn't respecting the character.
Opening Nov. 17, Justice League stars Ben Affleck as Batman, Henry Cavill as Superman, Amy Adams as Lois Lane, Gal Gadot as Wonder Woman, Jason Momoa as Aquaman, Ezra Miller as The Flash, Raymond Fisher as Cyborg, Willem Dafoe as Vulko, Jesse Eisenberg as Lex Luthor, Jeremy Irons as Alfred Pennyworth, Diane Lane as Martha Kent, Connie Nielsen as Queen Hippolyta, Amber Heard as Mera and J.K. Simmons as Commissioner Gordon.