Yes. First hand experience with a Dubai client's maid literally asking me "help sir I need go home". Through extremely shitty english she explained her girl back home was dying. Which she found out from her employer. Which would not give her passport back, but just informed her. Because yeah. But this doesn't count as a source. I thought it was a myth until I ran into it.

So literally pick any result off google for "modern slavery in UAE" "slavery in Saudi Arabia".

Here: moroccan, contract slavery, more, yet more because this seems implausible to you and a more personal story.