Theres a mage casting detect magic on people in Gadgetzan and theres 2 issues with it:
1. If you dispell it, the guards attack you
2. If you have lightning shield on and the mage takes damage from casting detect magic on you, the guards aggro you. (Need actual proof, this was mentioned by another player)
3. Despite his spell being hostile and applying a debuff, the guards do not aggro him
This mage has been in Gadgetzan for hours now exploiting this and griefing the FP, hes been reported.