Im not exactly sure this is considered an exploit, however in my specific case after you faction change, you have access to all of the flight paths.
As an example, Previously for somebody I'm power-leveling, their character was previously an Alliance Hunter(Night Elf I believe), After their transfer, It is now a Goblin Hunter, Regardless of having 0 quests done in Outland, Said character has ALL Outland flight paths. Im unsure if this works for all zones including Azeroth and Cata zones as well.