The bug:
1) Target a pvp flagged player or a mob
2) Turn on auto attack
3) Hover your mouse over someone (Any faction, don't need to be pvp flagged)- DON'T CLICK THEM-
4) Make sure you're in range of the person you're hovering your mouse over, you'll start auto attacking.
Hopefully I've explained it well enough, this doesn't work for spells, tested on ascent rev 3850, also note that this DOESN'T flag you for pvp, havent tested to see if it pvp tags you if you use it to attack someone who is pvp flagged, though (but why would you? ;p)