A proverb meaning that bad deeds or bad rumors spread quickly (bad news travels fast).
会社の不祥事はすぐに社外に伝わり、まさに悪事千里を走った。
The company's scandal was quickly leaked outside and indeed the bad news spread fast.
悪事千里を走ると言うから、まずは誠実に説明すべきだ。
Since bad news travels fast, you should explain things honestly right away.
小さな不正も放置すれば悪事千里を走る恐れがある。
If small wrongdoings are left unchecked, they may quickly become widely known.