Bomb Planted Medal

From Halopedia, the Halo wiki

Summary

Awarded after you plant the bomb in the opponent's base in an assault gametype.

The Bomb Planted Medal is awarded for planting a bomb in an opponent's base. It is available in all Multiplayer Assault gametypes and has a Bungie difficulty rating of 6 (out of 10). It is represented by a red inverted triangle with a bomb.