The reality starlet, 19, can be seen posing in just a nude crop top and matching thong, with what seemed to be a deep gash running down one cheek.
Her fans took to social media to query what the mark was, asking, ‘What happened to ur butt?’, ‘There’s a fresh scar on your butt’.
Others speculated whether it was proof Kylie had – despite always denying the claims – had her derriere surgically enhanced.
One person shared: ‘That’s the cut wear she got the implants in.’
However, the marking in question is simply a tattoo, inked in red, which reads ‘before sanity’.
Kylie got the ‘sanity’ tattoo, spelled ‘sa-nə-tē’ in 2015 and later decided to add the word ‘before’ to it.
The teen posted a series of sexy Instagram shots on Thursday, all of which showed off her slender waist.
With fans questioning whether the 19-year-old had shaved a few inches off in post-production, the star did her best to show she really does have the shape she purports to have.
The star kicked off her social media defense by posting a photograph taken of her by her go-to photographer Sasha Samsonova.
The previously unreleased professional snap does not show the top part of Kylie’s face but showcases her famed lips and curves.
In the image, Kylie shows off her slender waist and ample derriere in just a pair of nude underpants and a matching cropped top.