Fluke
Chance
紛れる means "to be diverted." A thing that is diverted goes in another weird direction. It's just a fluke or chance.
まぐれ
まぎれ
One reading does follow the 紛れる reading. But the more common reading is まぐれ. Very similar to まぎれる, but the ぎ goes to ぐ.
そのクイズの答えが当たったのはただの紛れです。
It was just a fluke that I was able to answer the questions on the quiz.