Substitute Craig Farrell scored with his first touch against his former club as Telford grabbed a late winner.
Farrell had only been on the pitch two minutes when he reacted first to a shot which came back off the post.
York had most of the chances, Jason Walker firing over from close range and then shooting wide after Lanre Oyebanjo’s pass.
But Farrell made his old club pay with an 87th minute winner.
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