Wierd Yellow Highlight

I got this “**yellow highlights”** after copying and pasting my block. Why does this happen? What is the solution?

thanks

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https://preview.redd.it/461romlhgn0a1.png?width=759&format=png&auto=webp&s=66f866cd1eac16ac596784139352faa4d0876c7a

 

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