Fox Trickery
Whenever a foes drops his guard, you can make him suffer with a dirty trick.
Prerequisite: Int 13, Combat Expertise, Fox Insight†, Fox Style†, Improved Dirty Trick.
Benefit: While using Fox Style, you can perform dirty trick combat maneuvers (Pathfinder RPG Advanced Player’s Guide 320) as attacks of opportunity. If your Intelligence is at least 19, you gain a +4 bonus on dirty trick combat maneuver checks.
Source: Ultimate Intrigue, p. 84