Bukkit

What is the issue? I had a new player join my server and he had $0 and he wasn't op or anything. Like a new person, so… he typed /rankup and it ranked him up…. so somehow it ranks people up for free… is there something wrong with my config or ranks.yml?? heres the ranks.yml:

#Note players must be in one of the ranks for the plugin to work.
ranks:
   default: 0 #This is the first rank
   a: 1,000,000
   b: 10,000,000
   c: 20,000,000
   d: 40,000,000
   e: 60,000,000
   f: 100,000,000
   g: 200,000,000
   h: 300,000,000
   i: 600,000,000
   j: 1,000,000,000
   k: 2,000,000,000
   l: 3,000,000,000
   m: 4,000,000,000
   n: 6,000,000,000
   o: 8,000,000,000
   p: 15,000,000,000
   q: 20,000,000,000
   r: 30,000,000,000
   s: 40,000,000,000
   t: 45,000,000,000
   u: 55,000,000,000
   v: 65,000,000,000
   w: 75,000,000,000
   x: 85,000,000,000
   y: 90,000,000,000
   z: 100,000,000,000
   maniac: 150,000,000,000
   criminal: 250,000,000,000
   thief: 350,000,000,000
   thug: 450,000,000,000
   monster: 600,000,000,000
   smuggler: 800,000,000,000
   robber: 1,000,000,000,000
   outlaw: 1,500,000,000,000
   gunny: 2,000,000,000,000
   bear: 4,000,000,000,000
   hitman: 6,000,000,000,000

Please provide any additional information below. Please respond as soon as possible.. thank you. Also, i have all of the ranks made and working.. i also have vault… please help.