Spreading Malediction

Spreading Malediction (previously Exploit Weakness) is a  passive skill, unlocked at level 38.

In-game
This skill provides a non-multiplicative damage buff for every enemy affected by one of the three curses, regardless of skill rune:
 * Frailty
 * Leech

This applies even if curses are bestowed by other items and skills, such as Cursed Scythe or Cursed Form.

Note that there is a maximum of enemies that can be cursed at once. Each enemy will only provide 1% bonus, even if more than a single curse is applied to them.