Revealing technical details to a competitor is no different from welcoming the flood through your own wall.
Tips
history
From 文康's Qing-era novel 《儿女英雄传》('A Tale of Heroic Lovers'), Chapter 4: '这不是我自己引水入墙，开门揖盗么？' - 'Isn't this just channeling water through my own wall and bowing thieves in through the front door?' Often paired with 开门揖盗 ('opening the gate and bowing the thief in').
usage
Used to scold someone, often in hindsight, for an action that handed an enemy or hazard direct access. Stronger than 自找麻烦 ('asking for trouble'); the water imagery suggests a flood you can't take back.
