It'll be safe if they don't put a carpet down or box it in.
Let me guess - under those stairs is a cupboard with the meter & CU, when you turn right at the top of the stairs it's bathroom & WC, and that cable is for a shower.
When built the cables for lights and sockets were buried in the wall, diagonally up and emerged under the toilet floor.
But apart from the cable my stairs look a lot like that right now, as we took the carpet up and have yet to do the refurbishment which is the next stage.
All the cables I have which run to the first floor are now boxed in and run up next to the newel post on the inside of the turn in the stairs.
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