In my world when I was exploring I suddenly found some blocks of nether rack in my over world in single player and there was a broken nether portal and some gold blocks when I broke a gold block suddenly all the trees were started burning all around me

That’s A ruined portal. Definitely intended.

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We're tracking this issue as MCPE-81330, so this ticket is being resolved and linked as a duplicate.

That ticket has already been resolved as working as intended, which means this is not considered a bug and won't be fixed. Please do not leave a comment on the linked ticket.

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