It is no longer necessary to take pictures in order to win photo contest. Photographers who share their images on public domain sites are sometimes surprised to learn that others have taken their images, entered them in photo contests and won awards.
Sasin Tipchai, a talented photographer from Thailand who shares his images on Pixabay with a CCO Creative Commons license for “editorial use only” and “No attribution required” was surprised to discover recently that a Swiss photographer named Madeleine Josephine Fierz had entered at least two of his images in photo contests and won awards.
It appears that Fierz make various digital edits to the photos prior to submitting them to the contests, from flipping them horizontally to inserting things like elephants and hats into the scene. She believed that because she had made minor changes to the photos she could claim the creations as her own.
For more information about this see this
Petapixel story.