And it's not a double sharp.
I saw it in Miley Cyrus Fugue in measure 88 between the 3rd and 4th beat for the right hand. It's being reached at 2:42-2:43 in the video and I don't hear anything special. Here is a screenshot for convenience:
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Added image description; Added link description and specific timestamp
200_success
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What is an X symbol appearing in a piano part?
user1803551
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