Vulnerable is a negative status effect and a battle mechanic that appears in Sonic Chronicles: The Dark Brotherhood.
In gameplay, when a target is inflicted with Vulnerable, he/she takes more damage when receiving an attack from enemies. Targets inflicted with Vulnerable are signified by dark green orbs hovering slightly above them.
Vulnerable can be inflicted on both playable characters and enemies when they are hit by certain attacks, such as POW moves or regular attacks (in the playable characters' case). It can be cured by Iron Tonic, Antidote, or Cure All Spray.