The material below is Open Game Content from a 3PP Source
Vulnerabilties (Ex or Su) A creature with vulnerabilities takes half again as much damage (+50%) from a specific energy type, regardless of whether a saving throw is allowed or if the save is a success or failure. Creatures with a vulnerability that is not an energy type instead take a –4 penalty on saves against spells and effects that cause or use the listed vulnerability (such as spells with the light descriptor). Some creatures might suffer additional effects, as noted in their descriptions.
Format: vulnerability to fire; Location: Weaknesses.